Hope you come back and let everyone know what the insurance company(s) decisions are.
I agree with the poster that said first check with the tow vehicle insurance policy, then check with the TT insurance policy if the TV policy did not cover. Since the vehicle was moving, to me, that points to TV policy being engaged first. Had a tree fallen on the TT after it was parked, then the TT policy should be contacted, since the TV was no longer in the equation.
Who was doing the spotting is immaterial. The TV operator was in control (and is the individual/vehicle insured).
Mike