Recently I started a job at a local Museum. The main building was built in the 1800s (old for California).

One night, myself and my coworker locked up before going home. We locked a set of two doors between the main building and the yard, and I gave the door a little shake to make sure it was latched. They're historic doors in a historic building, so they can be a bit finicky. My coworker watches me check it amongst all the other doors and lights, cuz I'm the new employee, and he doesn't want to have me accidentally leave something open or a light on. Then we leave and lock the gate to the yard behind us. The next morning the custodian finds the doors open, not just unlocked, but open, swinging in the breeze. My coworkers arrive a minute or two before me, so they get the custodian's note first and let me know. I go around and unlock everything else and turn the lights for the exhibits on. I find the light in the Judges' Chambers up on the second floor is on. Nothing is stolen or missing or even just displaced from where it should be. Everybody asks around to every other person who has keys, and nobody was there that night. We check the security cameras, and all they show is me unlocking things in the morning. My coworkers think it was one of the Judges ghosts from the 1800s. Unclear as to which one.

I think there's still some logical room for somebody with a key to have shown up for some reason and unlocked the doors and not shut them fully. It's honestly weirder to me that they would go into the Judges' Chambers, a dead-end room, and turn the light on.