Sorry, I haven't been on the board much lately.
This is what you need to do. First of all make absolutely certain he is not in your house. I know, I know you have checked, but you need to check again. This time you check on the premise that he is injured and unable to call out to you, or scared and can't get to you. Go into each room, and do the following- shut the door. Then lay down on the ground on your stomach. You want to look all around you- make a grid of the room, and search every inch. You don't search in hysterical mode, you search slowly and carefully and you just keep breathing deeply. You carefully turn over furniture, look for rips in the fabric where he could tunnel through. You empty out closets and drawers, look under chairs. Do you have a sofa bed? Cats are notorious for hiding inside the box springs. Don't say to yourself that he can't get in there, they can get everywhere. You want to look in your appliances as well, washer, dryer, dishwasher- move the refrigerator out and look behind that, look under the stove, or back behind it- LOOK EVERYWHERE
Once you have determined he is not in any room of your home, then you go outside- www.lost-pets.org
will guide you with all you need to do. But first, make absolutely certain he isn't in the house, injured.
Good luck- I am pulling for both of you-