There are some low end exceptions but for the most part every vehicle has a Vehicle number or chassis serial number. THis includes Cars, Trucks, Motor homes Trailrs Car dollies BICYCLES Basically anything designed to roll down the pavement. .or fly, or float (Boat hull number)
THey can be traced.. IF you can find 'em.
Your local or state police Auto Theft Devision is a good place to ask for help.
BUT WARNING. if it's hot. Well since you are not in possession you are safe. but the poor guy who was offering for sale may be in at least warm water.