I'm not surprised with those hits. Heart shots often do not produce a great blood trail because if you destroy the heart it quits pumping, which means there is nothing to force the blood out of the deer. A single lung shot is not that great either. I shot a deer with a bow once and got a single lung and hit the heart. The deer ran quite a ways with a very sparse blood trail.

Something you need to keep in mind when hunting, even with a gun is where the exit will be. I always aim for the exit wound, not the entrance. Much more important with a bow, but I still keep it in mind with a gun ( I use shotgun or ML, no centerfire where I live). So you need to look at some pictures or diagrams of a deer anatomy and picture different shot angles and where the bullet path will go.

I personally like a bullet that will exit the animal. I like one that will expand, but not so much that it will stay in the animal. Pass through shots normally will give you a better shot at a blood trail. Or from what I have been told you can aim for a high shoulder shot and it usually anchors the deer where it stands. Never tried it to be honest though.

Paul