It is told that the great magician Houdini, who was able to escape from even the most secure locks, chains, and bolts, was once challenged by the warden of a prison that he had an escape-proof cell from which even Houdini could not break free. Houdini promptly accepted the challenge, and after escorting him into the cell, the warden closed the cell door, leaving Houdini to his own ingenious devices.
Houdini took out his tiny tools that he always kept with him and began working on the lock. Although he was usually able to throw open any bolt within fifteen seconds, he now found himself frustrated. He then thought a bit, and tired a different technique. When the latter failed to open the lock, Houdini began to worry that he had finally been vanquished, and began working on the lock very feverishly, all to no avail. Exhausted and frustrated with his failure, he fell against the cell door, which swung open! The door had never been locked!
The point of the story is that even the great Houdini could not possible open a lock that was never locked in the first place.
Taken from Let Us Make Man by Rabbi Abraham J. Twerski.