I'd say technically it was the driver's fault for taking the truck someplace without enough ground clearance.  I have a truck that would probably be a problem that way.   But if I were the manager I'd go to the owner and say something like "The insurance company is probably going to say it is not our fault you didn't have enough ground clearance, especially since everyone else had been using it and not having problems.  But let's turn it in and see if they will help with it."

Kind of makes it plain the fault really is the truck's, but also shifts the blame for being hard nosed on the insurance company.