Don't give up hope. I've never lost a dog, but I've had cats go AWOL for weeks. One was a very weak and sick young thing someone stupidly let out while I was at work. He was just back from a week at the vet on IV, very thin. I had also just moved to a new house. The old house was about 3 km. away in a maze of busy streets. I called the new people at the old place, just in case he made it there, but three weeks later I was mourning. And they called me. They had a skinny little cat trapped in the porch. Off I went, and collected a scraggy bag of bones who spent the next month on my lap getting fed nutrient pastes. He lived to be 17.