If a camper is being towed by a truck owned by someone else whose insurance must cover liability for the camper the truck owner's policy or the camper owner's policy?

When I bought my new camper, my agent told me that I don't have to insure the trailer for liability because the liability extends from my vehicle policy.

Although your situation is different, I'd guess that whatever is pulling the camper is also providing the liability insurance. I'd call your agent.