Very little I can say that has not been mentioned to make you feel worse.. (just kidding) It happens. I've been lucky over the years in find them or in one single case, where someone else did and took it. Still, if it was a high lung hit, you might have hit that area above the lungs and under the spine. That deer will not die, but you did slow it down.

So don't beat yourself up. Next time aim a little lower... Actually because of my ability with open sights at any real distance, it is one reasonI have been transitioning to the 1x scopes. I think they are just a better aiming device for me.