I feel sorry for the boy.
If it was clear that it was an honest mistake, the police won't prosecute. These stories happen in a lot of families in non stressful times. If there's a 5 car caravan, the family may assume that he's in another car.
The parents, well I can empathize, but the kid will tell this story for a lo-o-o-o-o-ong time.
On the most inopportune occasions...
Jesus' parents left him when he was 12 - they didn't notice for almost a day!