Hi Cheryl,
First, keep the faith. Many basenjis are fearful of humans, so even though you haven't heard news, there's a wonderful chance that he's alive.
You mentioned that he's chipped. Have you contacted the company that his chip is registered with, so that they know to look out for him? Also, as a word of "warning", do not advertise that he's chipped. When I adopted Sophie, the vet asked if she was chipped and when I said that I didn't know, they scanned her and found a chip. After several heartwrenching moments, we discovered that the chip was sold to an on-line vet and no one knew where the chip was eventually placed, so there was no path to follow. IF someone wants to keep your boy, but doesn't realize that he's chipped and takes him to the vet, then you want to hope that the vet is a good steward and looks for a chip on the first intake visit.
Lastly, keep in mind that many people don't recognize these dogs as basenjis…. it is an uncommon breed.
Place ads that are generic in nature, i.e "lost black and white terrier".... this may bring more responses?
My thoughts and prayers are with you!
Patty