I just went through the same thing. I had to back out and come back the next day. I looked for hours, found it (half eaten by coyotes), and dragged what was left out about a half mile. I personally feel if you shoot it, keep at it. It may be tough and hard work but get it, you shot it. Unless you lose the blood trail after looking for a long, long time. If you know where it is (approximately) you owe the game and yourself the respect of making every single effort.