That is the best kind of stolen bicycle! I've had a similar experience in college. I gave the keys of my motorcycle to a friend, who needed to go home to get his assignment. I told him the plate number - 1234. He assumed that I meant the 4th bike in the line, unlocked it and took it home. We only found out what had happened when he got back - he wasn't able to lock it, the key wouldn't work. So we left it unlocked and hoped for the best!