Now, in the fine print, is there anything about a maximum amount that they will pay for damaged "cargo"?
Seems like cargo would be considered personal property which generally isn't covered on an auto policy. I agree with you that if there is coverage for personal property it would be limited to items like luggage, clothing, CDs, or vehicle emergency equipment. Then you have your deductible which would wipe most of what might be covered. Rustyshackleford55 did the right thing by obtaining a stand alone policy for his camper.