Any blood trail at all? Usually this hit produces little if any blood. I killed a buck one year with the same hit. There are some very large vessels in the hams. You may want to go out tomorrow morning and look the area over real well concentrating on a crisscross of the area that you last saw him traveling. The buck I killed made a large circle and ended up dying about 20 yards from where I shot him. I let him go about 1 hour and when I decided to start tracking, I took 2 steps, heard a stick crack, turned and watched him walk up to within 20 yards and crash.