Without further information regarding the amount of damage, the type of damage and what the OP is seeking in Diminished value it is nearly impossible to offer advice. I don't even know if Carfax or a similar service even offers reports on non-motorized claims. If they do, I don't have a clue if they capture 99% of claims or 1%. Once repaired, no one may ever know a claim ever happened.
Repairs do not automatically reduce the value of a vehicle (or travel trailer). It would be a mini lottery win for me if someone hit the rear of my truck. I might get a new bumper, a new tailgate, and maybe even a new bed to replace the ones beat up by hauling gravel, concrete blocks, pallets of sod, multiple tons of garbage and everything else under the sun. The story is different if the damaged vehicle is a new Bugatti. Unless there is way more to the story, if the damage is cosmetic, I would move on once the damage is repaired. Five years down the road, the only thing that is going to matter is current condition.