I was kind of thinking that - looks like you guys put in the effort to find him and just couldn't do it, your nephew will learn from this. These are good experiences and he will become a better more ethical hunter because of it. Looks like you tried to teach him how to do it right as best you could and he just made a typical human error on the shot placement.
I had a kind of similar event happen to me when I was 17 on a rifle hunt. I was sitting over a canyon from the rim watching the sun rise and heard some shooting and yelling coming form the other side. I saw the hunter running through the trees first and then I saw the buck come running out with his guts hanging down from a huge hole in his side. It was clear that the wound was fatal, but would kill him slowly. At the time, the area I was hunting was a 3 pt. or better area and this buck was a nice big 2 pt with a barely legal 3rd point on one side that I could clearly see shining in the early sunlight as it bounced across the canyon. I yelled to the hunter, who was about 30, and told him where I could see his buck and that it was going to come right by me. I asked him if he wanted me to help him put it down and he yelled back "yes". So I had a great broadside shot so I took it and hit him just above the heart but took out both lungs. Well the buck didn't go down as it was already surging adrenaline, but I knew the shot was good and sure enough, when the guy got over there we began tracking the buck and had a really good blood trail, with good frothy blood and pieces of lung. I told the guy that I would stay on the track and that he should head down the bottom of this side canyon / wash where the buck was headed in case I pushed him down to him. He agreed and we split up. About that time I heard someone from the other side of the canyon yell "RUSSELL!" and I asked the guy if they were yelling for him. He said that it was his dad and that he would answer him when we found the buck. Well, we split up, I went high following the track and he went low and sure enough, the buck was heading for the bottom of the side canyon / wash and I thought for sure we would meet up at the dead deer. I kept on tracking the buck until I found him but when I got there, "Russell" was no where to be found. Apparently, he had seend the buck from the bottom and began to question its legality and sneaked away like a coward.I even yelled back for him, but got no reply. So there I am, a 17 year old kid all alone with a dead, barely legal gutshot deer that wasn't mine. Well I began to take care of the deer and pretty soon my dad came and found me as he had heard the shots and the yelling. I told him what happened and he went back to the canyon rim and began yelling for "Russell" to come back and get his deer. He was pretty mad at the dude and wouldn't let me put my tag on the deer. We took care of the buck and hung it in a tree as the weather was pretty cool and the meat would keep fine. Then we went drving around to a bunch of different camps on the other side of the canyon looking for "Russell" but we never found him. Finally, we found a game warden and my dad told him what happened. I thought for sure I was going to get a ticket becuase the deer was probably not legal and because I didn't tag it after I killed it - even though I only ended its life earlier than the original hunter's shot would have. I was just sick about the whole thing and would have taken the ticket too because I knew that was the most ethical and moral thing to do - even if my dad wouldn't allow me to tag it. But, the warden drove around to where we told him the deer was hanging and said he couldn't find it - so no evidence, no ticket. Guess he either didn't look hard enough, didn't really care about it, or didn't want to go on the same wild goose chase we had been on looking for "Russell", or he didn't think I was legally liable. Whatever the reason behind his decision, when he told me "no evidence" I was smart enough to keep my mouth shut and accept it.
I guess the warden gave me a break but I did learn some valuable lessons about ethics though. First - will I ever "help" another hunter finish off his deer? NOPE.
Will I ever help another hunter track his deer? YES - but I will make sure the cowardly bastard sticks around to see it through.
Will I "punch my tag" after wounding an animal - NO, not until I find him dead and can claim the body.
UTROY
Proverbs 21:19 (why I hunt!)