Have you contacted vet offices and low cost neuter/spay clinics? Since he is intact and someone may be keeping him, the finder may go and have him neutered.
Jennifer
In the old book/movie, "Goodbye My Lady", the basenji was lost and living in a swamp when rescued by the boy. Dexter was re-enacting that role, perhaps!
Don't give up hope; I thought one of my other dogs was dead earlier this year, (he's a deaf staffy); he was lost during the week of the blizzard… I said many prayers, and I live in a farming community, w/the help of a wonderful friend, and many prayers Jack made it home safely... a little thin, raw paw pads, but he came home alive (and yes the fence was fixed). I'll keep ya's in my prayers.