My experience is that shots which hit bone going in or coming out leave a decent blood trail. If you poke between ribs, exit hole is usually small.

High on the body will almost never leave a heavy blood trail, as it pools inside. My nephew killed a nice 9 point last week in Texas. I saw the shot, and watched the deer fall 30 yards away. Heart was totalled, didn't hit any bone, and there was zero blood trail. When we got to the deer, there was just a bit running down the off shoulder, but none had reached the ground