Long time lurker, first time poster. Given that this person blends in, does not appear to be a monster, and possibly helped with the search, could it be a DPW worker? In my small town, the DPW workers are known by many as they are also plowing, fixing roads, trimming branches, etc. and are usually close with the police and fire department guys (and sometimes are volunteers for these departments). The ones here play on the local softball team and seem like good guys. This could also explain "who was driving the vehicle" if it was a town water, park or highway department pickup truck/car used by several workers. A witness report of a town vehicle parked near the trails might have been dismissed early on in the investigation.