I pray for his safe return. I wish there was something I could do.
Is there someone the child knows (ex wife girlfriend etc) and trusts that he may have gone off with?
Has he ever been camping with anyone? Is anything missing from his room? Does he have a treasured object that he keeps (blanket etc)? If so is it there?
Does he have any money in his room? Is it there still? Has he every travelled alone before? Does he know how to ride the bus? Is his bike at home?
You need to think of people he trusts. Neighbors, friends, older friends, scout leaders, house keeper etc. Is there anyone that he may have seen recently?