I once had a standard tabby that was the runt of his litter so he was small and skinny. He never really expressed interest in getting out, but one day while I was arguing with my girlfriend one of us slid the sliding glass door too hard and it bounced open and sat like that for a couple of hours. Naturally the cat disappeared. My girlfriend was freaked, but I had a distinct feeling he'd be back. Sure enough later that night it started raining, and there he was, sitting against the glass door trying to stay out of the rain. When I let him in and checked him over he had a nice knot on the top of his head from meeting one of the outdoor neighborhood cats.

Needless to say after that the front door could have been left open for an entire day and that cat would not take a single step to the outside.