You ask a good question, OP. Also, you could also check to see if this legal owner has also paid off the camper before selling it. Wouldn't want a bank sending a repo man over to pick up what you thought you paid for, only to find out the lien on it from the bank is still in effect.
Same with some other big ticket items; My tractor for example. No registration of any kind, but I'm sure if Wells Fargo, who holds the paper on my tractor, didn't get paid for a couple months, they wouldn't care who 'thinks' they own it, they would take it.