The same thing happened to me a few years ago. Don't lose hope. My little 6.5lber was gone over 5 weeks. She is skittish and would never come to anyone who is "notthemomma" and then sometimes... not even then. ;-)
One Sunday morning, hubs opened the door and she just shot into the house. Well she look emaciated, but I know a cat will never come home if she is on deaths door, so I let her rest and calm down that day. I took her to the vets on Monday morning. She was down to 4lbs!! They put a couple of hydrating sacs into her and did blood tests and she was just fine.
The only thing I can figure ... is there was a vacant house for sale that I think she just got stuck in (garage maybe?) Heck, I don't know.
Just know that cats DO know their way home and if they possibly can, they will
