The bus is on a trail that leads directly back to the nearest town. And it's an east-west trail, so he would have known to go East.
You're constantly making decisions to travel to avoid trees, difficult elevation, brush which entails changes of direction. The inaccuracies in those decisions can compound. The idea that you can just look at the sun or have nothing but a compass and travel safely and confidently in unknown territory is a myth. It's rarely ever as simple as moving in a straight line.