The Great Adventure of Aaron Appelapolous

You search the entire cell, top to bottom, but find nothing. Eventually you start combing the walls, looking for any loose bricks.
"Eureka!" you exclaim as you discover a key behind a lose stone. Excitedly, you race over to your dungeon door, insert the golden key into the lock, and turn it.
It doesn't budge. You try it many more times, but the key doesn't appear to fit the lock.
You slump down on the dungeon floor in dismay.