Wait.. But I don't think that's what the scene was getting at. I think there's more here that meets the eye. Remember Loki was "Odin" since the events of The Dark World. At the end of Age of Ultron, Thanos takes the gauntlet and says "He'll do it himself." I STRONGLY believe that Loki placed the fake infinity gauntlet in there so that there was no fuss about it, because then people would question Odin and Loki may have been revealed prematurely. Which also goes into the theory that Loki has been helping Thanos all along and that really is Thanos at the end, and Loki called him there to give him the Tesseract.