I'm just going to throw this out there since I enjoy offering false hope, but if the dealer sold the truck as an AWD (in writing), and it turns out it is "only" a RWD model (that is, never had AWD, not just that the AWD doesn't work), then there could possibly, maybe, be a miniscule chance of a small amount of restitution that is in order. Of course, there is the whole "caveat emptor" thing to contend with, even here, but at least there is a glimmer of an argument to be made for the buyer.
(Actually, I just mention it since we have no idea why the trucks' front wheels aren't being driven. Odds are the AWD system itself is shot, but on that .1% chance it isn't...)