If you are buying a used bike, say off the craigslist, how do you make sure, or at least reasonably sure, it's not stolen?

My first instinct would be ask for a receipt, but then, I'm pretty sure I don't have the receipt for my bike any more.

My second instinct would be to not buy from slicksuzy@istealbikes.com, or anyone dressed like the hamburglar. But, then, if I was a bike thief, I'd just get an email address like nicebikelady@honestabe.com and just dress normal.

Do police departments provide info on recently stolen bikes? And if you live in an area like LA, where there are a zillion cities with a zillion PDs, do they even talk to each other?