We've had many cats over the years and sad to say that once they go missing, it's unusual to have a happy ending. However, we did have one that disappeared for three weeks without a trace and then one night, turned up at the back door. He had blood coming from his mouth and we rushed him to a vet who told us that he had probably been hit by a car earlier that evening.
So it seems, when he needed help he came home. I hope your cat comes home soon.