Travel Trailer History Report?

It also could have been as simple as sales staff using it to warm up their lunch and keep their refreshments cold.

Served as employee(s) break room or hangout maybe?

I think he is just SOL. As stated, never titled who knows what the dealer did. Maybe he let some use it over night as a test camper they were wanting to buy. You know, like rest driving a car? Folks are always saying that they wish they could test drive or test camp their camper before purchasing.

No buyers remorse. The food particles in he microwave and fridge are a good clue. And the dealer rents travel trailers.

He bought a "new" trailer sold as new? Did he do a PDI? Did he get a walk through? If it has never been licensed or titled who is going to have the information?
I suspect for some reason he is having buyers remorse. If thats the case, good luck.
To answer your question. Unless the RV had been licensed or titled somewhere no one is going to have any information.