Stashed the bike within walking distance - before he torched the truck...or...rode the bike over the truck tracks.
This guy is calculating - preplanned his whole vendetta down to the smallest detail. Definitely watching the TV reports of law enforcement wandering all over the mountain looking for him on foot and having a good chuckle.
JMHO
Yeah, he could have stashed a vehicle. I do think he probably planned for some contingency situations, but I read his manifesto, and the main impression I got was one of overconfidence, hubris, and bravado.
He may just have been laying it on very thick to psychologically intimidate the police, which is a good force multiplying strategy for him. Still, I get the feeling he is quite a narcissist and maybe he has bought into his own bull manure, thinking he could pull off more than he is capable of.