John Popp
Site Supporter
Get a large oral syringe, if you can't find one see your vet. Cut a portion of the tip off as you don't want them chewing it off and swallowing it. Be patient and start by trying to get them to eat 20ml. You might not be able to get that much in but that should be an initial goal 2-3 times a day. After finding success move to 30ml per feeding and really try to get 3x a day. It shouldn't be long after getting there that they'll be eating on their own.

I'm hoping you find him... Can you leave some food out for him and his litter box?