I had my two identical boys, markings wise but one ginger and one tabby, Pixel disappeared when he was about 5, they were littermates and I know he would have come back to Trouble if he could. The Council didn't find him on the roads, the railway workers on the line opposite didn't find him either. All I had to comfort me was hoping that as a lovely affectionate cat who used to sit at the end of the drive to greet people, someone who would look after him well had stolen him. We live near a train station and people park all down the road and maybe they lived too far away for him to return to us.
Microchips were rolled out a couple of years later and I have had my cats chipped ever since.
I refused and still do to think of the alternative. His brother was PTS three Christmases ago at the age of 18 so I know I'll never see him again.