Where did McCandless get a ticket?

Chris McCandless abandons his yellow Datsun in Lake Mead National Park after a flash flood. He burns all his money, buries his rifle and sets off on the next leg of his journey, hiking all the way to Lake Tahoe and the Sierra Mountains.
Chris receives a ticket for the abandoned car, which wings its way from California to his parents' house. Chris's parents are understandably concerned about their son, but at least now they have some information as to his whereabouts. With the ticket as evidence, they hire a private investigator to track him down. The P.I. is able to establish that Chris has donated his money to charity, but beyond that there's not much more information he can give. This isn't surprising as Chris is constantly on the move along the West Coast, from where he hopes to travel across the border into Mexico.