Why did Rico drive to So Cal in the first place? It would be a 16-hour drive if he averaged 70 mph. He left on Oct 9 and was supposed to be back in Seattle Oct 10 for a barbecue and had a job interview on Oct 11. Who plans a trip like that? It's crazy. And what did he do in Alhambra? He had dinner with his brother, talked to his mother, and packed up a few mementos. This was something he could have done any time - he could have done it the following week when he didn't have any engagements to get back for - or he could have asked his mother to pack up his mementos and mail them to him in Seattle. It sounds like he went to say goodbye to his family members and took his basketball mementos that represented the best times in his life. If he was truly trying to get back home to Seattle for the barbecue, he wouldn't have made the side trip to the mountains. It sounds like he could have been looking for somewhere peaceful to end his life. But, then, where's his body?
My other thought about the trip to Alhambra was maybe to buy drugs. He should have been able to find drugs in Seattle, but maybe he hadn't made a contact yet and thought it easier to do on his own turf. But this seems unlikely as there was only one bindle wrapper in the car.
The grandparents who found the backpack and cell phone... Were they just going to keep it? My husband has found two cell phones. On the first one, I dialed "Mom"and said we had found a phone that apparently belonged to one of her children and gave her my #. The guy called me and we dropped the phone by his house when we went out. I forget what happened with the second phone; maybe it had lost its charge; but we turned it in to the police dept. If I found a backpack with a cell phone along a road out in the boonies, I'd think that someone might possibly have been abducted, or been hit by a car and dragged off the road, and I'd call the sheriff.
Maybe it was a hit and run at another location and the driver pushed the body down an embankment and the backpack was left at the side of the road in a different location.