>So which Infinity Gems have appeared so far? Thor said four,
>and that's what I counted (Loki's, the aether, the mind gem
>and whichever one they had in GotG,) but as far as I can tell
>Thor wouldn't have any idea about the one from GotG. Is there
>another one I'm missing?

Loki's scepter held the Mind stone. So those two are the same. You're missing the Tesseract (Space stone).