I accidentally and recklessly quit to world select after beating Wacky Woods, the key isn't there when i open the world, but i didn't get it either.

Help! D: What do I do??

I don't have access to Dr. L at the moment so I can't look at the world in the editor, but have you tried completing the final level again? It's possible that the key appears right after you beat the final boss (possibly inside the level itself). If that doesn't work, I'll check out it out myself.