* Any extended warranties purchased: The original owner might have bought an extended warranty that could still be in effect (though this is unlikely after two decades). The terms of any such extended warranty would dictate the coverage.
* State lemon laws: Depending on the state where the truck was purchased and its history of repairs, lemon laws might offer some recourse for significant, unresolved problems. However, this is a legal matter, not a standard warranty.
In short, there's no factory warranty left on a 2002 F-150. Any coverage would be from an aftermarket extended warranty or potential legal avenues.