I got a big U-lock not too long ago, and promptly lost the keys a few weeks later (both keys still on the same ring). I'm pretty sure they fell out of my saddle bag when I had the bike flipped upside down to remove the wheels after a group ride, and left the bag unzipped. Went back to the same area looking for the keys but no such luck. Now I have an unusable U-lock hanging in the garage.