Jag kan tänka på följande skäl.

1. Voldemort underskattade helt Harry Potter

“One of us?” jeered Voldemort, and his whole body was taunt and his red eyes stared, a snake that was about to strike. “You think it will be you, do you, the boy who has survived by accident, and because Dumbledore was pulling the strings?”

Harry Potter and the Deathly Hallows, Chapter 36, The Flaw In The Plan

Med Dumbledore av bilden, trodde Voldemort Harry att gömma sig.

2. Voldemort var övertygad

“Accidents!” screamed Voldemort, but still he did not strike, and the watch- ing crowd was frozen as if Petrified, and of the hundreds in the Hall, nobody seemed to breathe but they two. “Accident and chance and the fact that you crouched and sniveled behind the skirts of greater men and women, and permitted me to kill them for you!”

Harry Potter and the Deathly Hallows, Chapter 36, The Flaw In The Plan

Voldemort ansåg att Horcrux var väl skyddad

3. Han visste inte att Harry och Dumbledore kände honom inuti

Dumbledore:

Well, as you now know, for many years I have made it my business to discover as much as I can about Voldemort’s past life. I have traveled widely, visiting those places he once knew. Harry Potter and the Half-Blood Prince, Chapter 23, Horcruxes

Harry:

“I think he would have envied anyone who had a key to a Gringotts vault. I think he’d have seen it as a real symbol of belonging to the Wizarding world. And don’t forget, he trusted Bellatrix and her husband. They were his most devoted servants before he fell, and they went looking for him after he vanished. He said it night he came back, I heard him.”

Harry Potter and the Deathly Hallows, Chapter 24, The Wandmaker

4. Horcruxes var väl skyddade

Horcruxes var väl skyddade antingen med betrodda vänner eller hålls på svårt att hitta platser. Utöver det var Horcruxes skyddade av charms.

Marvolo Gaunt's Ring:

I stumbled across the ring hidden in the ruin of the Gaunt’s house. It seems that once Voldemort had succeeded in sealing a piece of his soul inside it, he did not want to wear it anymore. He hid it, protected by many powerful enchantments, in the shack where his ancestors had once lived, never guessing that I might one day take the trouble to visit the ruin, or that I might be keeping an eye open for traces of magical concealment.

Harry Potter and the Half-Blood Prince, Chapter 23, Horcruxes

Salazar Slytherins ficka:

“Not here, precisely,” said Dumbledore. “There is a village of sorts about halfway along the cliffs behind us. I believe the orphans were taken there for a little sea air and a view of the waves. No, I think it was only ever Tom Riddle and his youthful victims who visited this spot. No Muggle could reach this rock unless they were uncommonly good mountaineers, and boats cannot approach the cliffs, the waters around them are too dangerous. I imagine that Riddle climbed down; magic would have served better than ropes. And he brought two small children with him, probably for the pleasure of terrorizing them. I think the journey alone would have done it, don’t you?”

Harry Potter and the Half-Blood Prince, Chapter 26, The Cave

Lägg till Vishveshs svar, Voldemort tror att endast han och bara han känner till horcruxernas existens och han är så nedsänkt i hans planer att han inte kan "känna" att hans horcruxer förstörs.

“Does Voldemort know when a Horcrux is destroyed, sir? Can he feel it?” Harry asked, ignoring the portraits.

“A very interesting question, Harry. I believe not. I believe that Voldemort is now so immersed in evil, and these crucial parts of himself have been detached for so long, he does not feel as we do. Perhaps, at the point of death, he might be aware of his loss . . . but he was not aware, for instance, that the diary had been destroyed until he forced the truth out of Lucius Malfoy. When Voldemort discovered that the diary had been mutilated and robbed of all its powers, I am told that his anger was terrible to behold.”

Harry Potter and the Half Blood Prince, Chapter 23: Horcruxes

Senare när Harry och Dumbledore börjar hitta horcruxen i grottan, försöker Harry stoppa Dumbledore från att dricka potionen för att hämta horcruxen, säger Dumbledore:

“I’m sorry, Harry; I should have said, he would not want to immediately kill the person who reached this island,” Dumbledore corrected himself. “He would want to keep them alive long enough to find out how they managed to penetrate so far through his defenses and, most importantly of all, why they were so intent upon emptying the basin. Do not forget that Lord Voldemort believes that he alone knows about his Horcruxes.”

Harry Potter and the Half Blood Prince, Chapter 26: The Cave

Inte riktigt. Nagini märkte låset men hon hade inte sagt det till Voldemort.

Jag kommer att svara från filmerna eftersom filmerna tycks ligga till grund för frågan.

I filmen ser Nagini (som Bathilda Bagshot) säkert ut på horcruxen. Det är klockan 1:30 i videon.

Horcruxverkaremitteraenotroligorangeglödavnågonanledning.Dettaförklarasinteriktigtifilmen,mendetkanvaraHorcruxsättattförsökaritauppmärksamhetmotsigsjälvinärvaroav(ännu)enannansjälsdel.Dettaärspekulation,dock.

DetärinteattsägaattNaginimärktedetsomsådant.SomJanusBahsJacquetmedrättapåpekar,harviingenanledningatttroattNaginikändeigenHorcrux.Honkanbarahablivittillfälligtdistraheradavettoförklarligtljus.Detfinnsingetomnämnandeavnågonstörrebetydelsefördettaögonblickpåthe final screenplay , förutom en omnämnande att horcruxen "ryckar" i Naginis närvaro .

132 INT. BAGSHOT HOUSE - BEDROOM - SAME TIME - NIGHT 132

Harry watches as Bathilda moves closer, transfixed by her milky eyes. The Horcrux on his chest TWITCHES.
(Harry Potter and the Deathly Hallows - Part 1 Screenplay, Page 94).

Det är kanske värt att påpeka att i böckerna ser Nagini inte alls locket. Det är fortfarande dolt under Harry's topp, även om det hoppar när Nagini kallar Voldemort.

I filmen kommer Voldemort inte att flyga över till Godric's Hollow i strävan efter Harry och Hermione som han gör i böckerna. Så han och Nagini skulle inte ha haft omedelbar möjlighet att prata. Även om de hade, det finns ingen riktig anledning till varför Nagini borde göra ett försök att säga, "Hej, gissa vad, Potter-pojken hade det här freaky glödande halsbandet. Kanske bör du kolla upp det!".

Nagini såg locket men hade ingen anledning att tro att det hade någon konsekvens.

Vad gäller dialogen i den efterföljande filmen tycker jag att det kan läsa för mycket i Voldemorts val av ord som han säger att horcruxerna är "vår hemlighet". Utanför universum, det här är bara Steve Cloves sätt att shoehorning Voldemorts tankeprocess från böckerna till talad dialog. Eftersom Voldemort bara dödat en massa människor har han ingen annan att prata med, så Cloves har honom att prata med Nagini. Det betyder inte att Nagini vet allt om de andra horcruxerna; hon är bara karaktären som var där vid tiden.

Voldemort: The boy has discovered our secret, Nagini. We must find out just how much he knows. We must return to our hiding places and see if the others are safe.
[Montage of images.]
Voldemort: And you, my friend, must stay close...
(Harry Potter and the Deathly Hallows - Part 2 Screenplay).

I ett universums perspektiv talar Voldemort i stenografi. Han internaliserar den brådskande uppgiften som är före honom: kontrollerar hans horcruxes. Han förväntar sig inte att Nagini ska följa med honom; han tänker helt enkelt högt. Naginis huvuduppgift, som med någon överklagande sidekick, var att sitta tyst och dö på sin herre - att inte faktiskt hålla sig i takt med sina onda planer.