Unfortunately, it is quite possible. Think about all the cases of people who have disappeared into ravines here in the states in CARS and weren't found, sometimes for years. Philip Taylor Kramer (the guy from Iron Butterfly) was in a MINIVAN and wasn't found for 4 years and that was near Malibu.
If the vegetation isn't deciduous, he may never be found.
It sounds like this might be the case. How sad. His father is staying until he is found and mother and brother may stay another week. Can't remember which article stated that but I doubt that his father can stay indefinitely. I can't imagine flying away and looking down knowing that you are leaving your child behind.