So, I'm stuck. Floor 4-3 Dark Temple. I had 2 keys, I'm guessing I was supposed to use both keys on 4-3, but used one of them on 4-4. I need the key for the bottom left room on 4-3 in order to progress any further on 4-4. I've went through every room several times backtracking but to no avail. Have I missed something or will I have to completely restart the game?
Edit: This is for the Knightin+ version on Xbox1.