Cats are amazing survivors so don't get discouraged. The GOOD NEWS is that unlike dogs, cats normally do not roam very far from home ... WITHIN a 5-7 house radius. Your cat is probably scared, but hiding nearby. Just know that after being outdoors for awhile, an INDOOR cat will go into a protective SURVIVAL mode and will probably NOT respond to YOUR calls ... even if nearby.
If you have a GARAGE, leave the garage door slightly OPEN so your fur baby can have safe access to return home. Place items with your kitty's scent along with STINKY wet food (tuna/sardines) and WATER inside the garage to help lure your kitty. If NO garage, try to leave those above items outside NEAR the door where your kitty EXITED your home.
Cats feel safest to come out of hiding when it's QUIET and DARK. One suggestion would be to walk around your neighborhood at night (between 10 pm - 2 am) shining a FLASHLIGHT and look for reflecting EYES ... beneath cars, bushes, decks and on people's doorsteps. As you walk with the flashlight, call softly for your kitty and SHAKE your car keys or cat treat bag ... a sound that your cat will recognize. It took thirty (30) days to find and rescue my friend's cat. She was hiding in the STORMDRAINS during the day and coming out at night. It just took forever to get any sightings of her.
Please ask your neighbors to CHECK inside/under their BACKYARD SHEDS, decks as well as their GARAGES. Cats have been known to get LOCKED inside a shed/garage after owners finish yardwork.
Also visit your nearby animal shelters IN PERSON. Don't just call as your kitty may be overlooked by the busy staff, so actually go there. I recommend visiting EVERY OTHER DAY, because after the required holding period, the shelter can legally adopt her out or worse (if injured/sick).
I hope and pray that your sweet kitty finds its way back to you. Please keep us posted.
Put his dirty litter box out ASAP, put out some wet stinky canned food tunafish is always great, something with your scent on it like a blanket put your that out, they come out at night mostly when it’s quieter keep calling him shaking treats leave the garage cracked if you can keep calling...