I'd check any hill or ridge. He's going to lay down and he'll want to see. I'd bet he's trying to go up, not down. He's going to die, there is no question. So like mentioned earlier, you're doing what you can.
One other thing I do when I track, is use my nose. I used to cut about 200 deer a year at my uncles butcher shop. And a dead deer has a smell (not a bad one, it's not a death smell. well at least not right away) that is very recognizable to me. Even 2 hours old, I can smell them. Just my lil trick. Found a doe for my dad with just my nose once. Then we found blood. After that we were both believers. Good Luck!