There seems to be a lot left unsaid behind your question; the comment that she "breezes in and out" does not sound neutral, and the reason you give is that you are going to possibly need to call the authorities? Does this happen with all of her boyfriends? The boyfriend refused to divulge his address and said he would call the police? Why don't you just call one of those places on the Internet that does background checks? They will get you his address, and it isn't very costly.
Sorry but Overprotective, I'm sure she wants to feel comfortable at her boyfriends house, and not thinking about how Her parents might be popping up out of nowhere or spying. I'm 23, I'm a boy, and my parents still do the same thing to me, that is an easy way to make your children feel uncomfortable and putting a wall between you and them.