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
update:
Ginny (Basenji lost in Dennis, MA) has been sighted several times, including by Cheryl herself, and is hanging around a specific area. A humane trap will be set up tomorrow, and her new dog-brother Tom is on the job laying down a scent trail for her. Keep the good vibes coming at them all, and keep your fingers crossed for good news in the very near future!
Laura Whitney
Arlington, MA
Thanks for the update MacPack. A great ending to the story. If you see Kaisers folks again, tell them we all send our well wishes to them and their dogs.