Ok I'm about to go out on a limb, but I think he is fine. Probably spending the days between a friend's house and outside. It will probably be a friend that the parents don't know all that well and would not think to ask. Seems like a good kid, I don't think he had specific reasons, more like teenaged hormones and some built up feelings of anger toward his parents for something, coupled with this friend possibly convincing him not to go home.
Best of luck.
