[Susan W]

Do you have anything that makes them squeek? Like a food bag? Mine squeek when they hear plastic bags because it sounds like a food bag. I would knock on all the doors near you and ask if anyone's seen them...and bring a plastic bag with you and crinkle it (loudly but discreetly) while you're standing in the doorway. They might just start squeeking from a back room somewhere, and you can see if the person looks uncomfortable. And if that happens, call the cops.

It might not work, but its something to try. I used to have some nice looking (in the friendly sense) college girls living next to me in my last apartment, and I was surprised to hear one of them say she wanted to steal one of my potted plants (heard it through the open window). It may be someone who lives very near you.