Since I've lived in Cambridge my car has been broken into twice. The first time was very obvious, window bashed in and everything. The second was more subtle because they just broke the lock on the passenger side door. If my car wasn't normally messy I would have noticed (and there hadn't been much in there at that time. I mostly learned my lesson). But since then I make a slight effort to park the car where I might see it at night from my window.
This morning in a fit of wakefulness I wonder Just what the heck would I do if I saw someone out there in my car?. Would I yell? I'd probably call 911. But I'd feel so weird being a visible shadow in a window watching it.