If you were given permission to move the truck, why did you not move the camper as well? What went into the storage unit? I would contact the campground directly, explain the situation and ask them how they want to handle it. There is a good chance that they have liability insurance for just such instances. Keep in mind, though, that this may be considered an "act of God" and not covered. It's chump change for most law firms and not worth their effort. There may be some relief through small claims court or something of that nature.