Ja, det gjorde han.
Baserat på bilder som visades på SDCC Comic-Con (lågkvalitativ kopia här ) ses Loki presentera Tesserakten till en skuggig figur som är mycket större än sig själv. En minut eller så senare ser vi Thanos bära en handske med en glödande blå sten inbäddad i knäet.
Så antingen återhämtade Loki Tesserakt från Asgards vrak innan han gick ombord på Thor's ship (osannolikt) eller han tog det från valvet när han gick förbi det (högst sannolikt).
Studiohuvudet Kevin Feige lämnade lite till fantasin i en intervju med Slashfilm
SF: And we also see Loki in that area. He walks by the Tesseract. When that planet blows up at the end, I assume that particular Infinity Stone is not on that planet.
Feige: You were at Comic-Con, right? Did you see the Infinity War footage?
Yeah, and Loki had the cube in his possession in the footage.
Feige: The story I’m about to tell you is nothing about the mythology, just about filmmaking, I was just talking to Hiddleston about this. When he shot that, he had the Surtur skull and he walked by and he looked at [the tessaract] but then he kept walking. And he left frame. And it was like that in the cut for a while. And nobody remembered the moment. It didn’t register with anybody. So we recut it so that Loki looks at it and then we cut away. When we showed that cut, it registered with people who knew what it was. Did he take it? He stopped, what does that mean? Which was exactly what we wanted the audience to do.
Kevin Feige Answers Your Lingering ‘Thor: Ragnarok’ Spoiler Questions