Firstly, I hope you do find your cat safe & sound, but take reassurance from the other ABers and my story. I had a cat that went missing, I did everything you did and then she turned up a week later. A few weeks after that she went again, in fact the longest she was 'missing' for was nearly six months! It was during one of her 'missing' spells that my daughter on her way to school saw her sat in the window of a house grooming herself - the house was about half a mile away from home. In fact she came back sometimes with a different collar on! Phoebe was very much a feline free agent yet her brother Joey never strayed further than the bottom of the garden. Fingers crossed he will turn up when he feels the need.