Did he ever respond to a box of dry food being shaken? Have you left some out in front of your house? Unfortunately, he may really not recognize you outdoors (cats are weird!) and even if your voice sounds familiar, faces blur to cats sometimes and smells are much more meaningful, so do leave food out for him, but let him get used to eating outside, try to get a feel for what time he's likely to show up, and then each day (after a week or so when the routine's established) very, very gradually bring the food closer to the door and if you can, leave the door open with the dish JUST inside, until he comes in and eats - but DON'T jump him, talk to him or anything yet, just let him get oriented and walk around (maybe days) without anything startling him, and only if he comes all the way in and YOU'RE able to close the door before he can leave, close it, but be ready for a huge explosion of noisy cat. Maybe you could have some of his toys, or fave blanket, etc. near the door too.