Not sure if anyone has brought this up yet, if so, I apologize. If people in the area had only seen the boy and the man in the past few weeks, maybe they are father and son, but drifters. Maybe the boy wasn't where he was supposed to, and dad had to get to a new job, which was why he was so angry when he pulled him in to the car. If they have left the area they may not realize how much time and effort is being put into finding this boy, they could be somewhere far away where this isn't receiving any coverage.
The fact that this boy hasn't been reported missing makes me feel that he probably doesn't have any family in the area. Also, if none of the children in the area know him, he can't have lived there for long.
ETA: If he does have family that have left him home alone for the weekend, we should be hearing within the next few day or so about a missing child. I'm really hoping this isn't the case, and this boy is actually fine and on the road with his dad.