I'm back to thinking he might have been driving impaired, wrecked his car, then freaked out. He probably assumed the police would have to be called because of the wreck, his parents will know the car was wrecked. This was not a fender bender where a made up story would be believable. He's in a odd location. Police come, your impaired, they will know, ask you questions, your car will be searched, they might also find illegal drugs. He's thinking this is going to be a huge mess- court, jail time, school down the drain, parent disappointment, etc. I'm not saying all of these things would have happened, but he might not have been thinking rationally.
This is a young person, who maybe in that moment made a rash decision to leave it all (doesn't want the drugs on him) and walk off on foot, with no plan. My speculation stops there because what happened next? I would like to think he's hiding out alive somewhere and just doesn't know how to get out of this because it's just a big story now, LE is involved, parents are sick with worry OR he got into trouble overnight and has passed, waiting to be found, foul play (this is low on my list). IMO