The person who said he’s probably hiding in your yard is close to the truth. Most indoor only cats that get out are found within a 3 house radius. They hunker down somewhere like under your deck and cats have a “shut down mode” they can go into for a couple of weeks. Won’t make a sound and can survive on little food and water. Search with a high power flash light that will pick up his eyes if he’s in a dark hiding spot. I hope he’s home soon!