I would not let the cat outside again, we don't. After being a loyal indoor/outdoor cat, our two-year old Nebulung came home with the same kind of hair loss but with a deeper and longer (2 inches) wound and we could see his bones and meat. After a call to a vet, we were able to confirm that he wasn't bleeding profusely and was just laying there, in his comfy spot, showing us his wound. He allowed us to treat his wound with water, hydrogen peroxide, and a spray bandage designed for both cats and dogs. After nursing his wound, it closed up after about a month and his hair around the wound grew back. After two months, he was happy just to look out all of our open windows and big screen doors, and he even catches critters if his prey dare to come close to the two inch openings under our steel screen doors.
We are convinced that a human tried to slash his throat either with a knife, a weed-eater, or perhaps he was caught in a car fan and escaped.
Gray the Cat, is Indoor for ever now and he is extremely happy. On another board, I read that any cat would be happy just live another day. Gray is here. He's fine.
Love this Board!