Purchasing used...how to know if it is stolen or not?

According to my wife a former banker, there may be a paper trail for non registered/non titled campers out there, depending on how it was bought.
Cash deals- it's just personal property.
If it was sold with a secured loan the camper would have a UCC lien that is then filed with the state (this is from a few years ago, when we lived in CA). Of course the lender just could have made it an unsecured personal loan, in which case its pretty much the same as cash.