Well, I diverge from the bell curve and disagree. Only if you are willing to put that much leg work into retrieving a legitimate title and only if that much effort is worth it to you, then pursue it.
Personally, if the current possessor of the property cannot produce the title, I'd never accept it. There are plenty of "fixer-uppers" out there where the owner will have the correct paper work. Move on to the next one. Use your resources and time for rebuilding the camper, not tracking down paper work to make it legally yours.
The seller has the responsibility to provide the paper work. Have the seller track it down ... then make an offer to buy it. You should not have to do this type of work.
You already stated your state is strict with other vehicles that are road worthy. An RV / camper will be equally as tough. Why bother. You already have your answer. It will be a lot of work and probably still end, only in frustration. There ARE other campers out there that are equally as worthy of your time, talent, and resources to fix up and make beautiful again.