I used to swim at a JCC where very few people locked their lockers. One day I came back from my swim to find that someone had put a lock on my locker! I ended up having to tramp upstairs in my bathing suit to talk to the building manager about getting the lock cut off, which was a bit embarrassing due to the 30 Orthodox rabbis present in the lobby. The manager decided the we had to search every locker in the room (maybe 200?) to make sure that my things hadn't been moved before she could cut the lock. She and the staff thought that the lock might have been put there by another patron who had dementia; she was known to do funny things like that. After that incident I started requesting a lock when I got my towel at check-in.