If he was living in his truck, I would think LE did learn a lot from what was left and what was taken. Did he take a good bit of his clothing with him? Did he take his ID or cash? Did he make an ATM withdrawal recently or did he leave his money he did have in the bank. Was any cash left behind? If he had any sentimental items, did he take those or leave them behind?
I would think initally he could have covered a great distance, but the adrenaline will wear off and he would likely "crash" and have to stop to sleep. Just because someone can survive "off the grid" doesn't mean they can sustain themselves well if they are moving around a lot. The more he moves, the more he will need to consume to continue to fuel his body to keep moving. Look at those through hikers that do have supply stops and that come into towns to eat. They still lose a lot of weight and it's very intentional on their part to try to replace calories lost so they don't get weak.
Just some random things I was thinking. He might have gotten pretty far on adrenaline initially, but I do think he likely had to slow way down and maybe he went to a place he was familiar with. I hope that is the case. Continuing to move around will wear him out and if he can't really go into town to get food (and with what money?) then he might get desperate and do something erratic if given the chance, like break into a house or try to steal (if he manages to get himself near a town without being caught.