Thanks for the input! I should have made the keys more clear. I intend on making the full game into a dungeon crawler/vania game. I was trying to have as little prompting from me as possible. I really wanted to make the entire game without any language in it at all, but crunch time slowed me down.
I don't think the backtracking is necessarily bad, just I should have conveyed that it was a possibility. Maybe a sign in the first room that says find the keys?