Has he shot the gun since to see where it is hitting???

My guess it that the deer was actually slightly quartering away and he hit him "in the shoulder" with the bullet actually hitting a little too far forward and not going into the chest cavity, but knocking him down only to have him recover...I've seen this a time or two with some of our hunters, with another hunter killing the deer a week or two later and finding that he was wounded...

These slight angles can be tricky, with most hunters not realizing that they need to aim for where the bullet will exit, not enter...It can also be compounded with shots inside 100 yards if the hunter doesn't take a rest...