I bought a dog and asked him to wait for me on the road while I was clearing out some cave. When I came back out, I couldn't find my horse or my dog. I found my horse when I fast-traveled to a town, but the dog was gone. I went back to look for him in the same place, but he wasn't there. I fast-traveled to the town where I bought him, but he wasn't there either. Is he gone forever, or is there some way to track him down?