About to leave, truck batteries are dead question

Yeah, start with checking the battery’s voltage. Disconnect one of the cables on each battery and check each one separately.

Are there any accessories connected directly to either battery?

Normally on Ford’s, the 12v charging circuit from the truck is running through a relay that isolates the camper from the truck when the engine isn’t running. It’s not hard to defeat that though of you want to. As joerg said, make sure it’s not the camper that ran the truck batteries down.

:):)