You just need to get into the right frame of mind and there is nothing that a cop can/will do except maybe make you leave if the property owner insists.

I'm renting now, if I lose the contract, which I may have, I'd be in the exact same legal situation as you (provided that you are not caught in the act of breaking in). Living where you are not permitted is a civil matter and the ultimate penalty is eviction.

I've hardly thought about this at all, but there are plenty of things you can do to help yourself. Figure out the name of the owner, can't be that hard, maybe it's on the mailbox, maybe it's on the internet. Say that you have a cash deal with Jerry. Act like you live there, dust the place. If it seems stable maybe turn on the internet and pay the bill. Don't feel guilty, improve the place, don't damage it.

I'm not saying you should definitely do this, only that it isn't impossible or a terrible idea like you think.