So he's an outdoor cat? And black to boot.
How long has he been lost? What have you done to find him? Have you put up posters all around your neighbourhood? Have you put his litter box outside along with food and an article of clothing that smells like you or the member in the household he is the closest to? Have you gone out very early in the morning - 5ish - with a bag of his favourite treats and a flashlight to look under, in, on top of everything you can imagine a cat hiding under, in or on top of? Even trees. Have you asked your neighbours to be on the lookout for him? To check their sheds, garages, garbage containers. Have you gone to, not phoned but actually gone to, the shelters in your area to see if he has been brought in? Ask also to check the feral rooms as some cats "act feral" when captured and will put up a fight. He would then be put in that room. Act fast. They are the first to be put down. You need to check with the shelters every day. Last, have you phoned your town works department or whoever is responsible for removing dead animals from the roads. I know you don't want to think of it but it is a possibility. They don't bother checking for microchips or tags normally.
Good luck. Let us know.
Assumptions do nothing but make an ass out of u and me.
We can stick our heads in the sand for only so long before it starts choking us. Face it folks. The pet population is bad ALL OVER THE WORLD!