I must be fortunate as I have all pass thrus, however my uncle a few years back had a similar story as yours but only with his Semi-Auto Winchester 12 guage. He had a doe about 10 yards and he acted quickly and shot her with his slug. I offered to dress her out as he has slight arthritis and cannot hold a knife like he used to. The entry hole was as expected but there was not exit hole. I have seen this gun blast apart trees and it did not add up. I rolled her over and see a hugh knot in her side. There is the bullet. I was mistaken as it was only half of the slug!! The other piece was in the heart and it had tore it up pretty bad to render it useless. The ribs were broken apart as if Rocky was hitting them. The point of entry was right behind the front leg (I am amazed he made that shot with the arthritus). The only reasonable thing was it hit the ribs and broke and a piece went towards the heart and the other continued on path from the shot and did not have enough force to get through the hide. It was amazing and we still have that slug in pieces on the shelf in the hunting trailer and talk about that every year.