Maybe if there was just one locker that WAS labeled? Like the very first locker when you enter or something.
Viewing post in What did you think of the lockerroom puzzle?
Feasible even, that somebody kept forgetting which locker was theirs and doodled either the code for their locker or some other hint on it. Actually, some scribbles could even be hints about the character a locker belongs to instead of hints for the puzzle, make people want to take a look at them regardless. Just a fun idea!