A bowhunter I knew of in Michigan hunted with his bow for a couple years for a huge buck. In the second year of the hunt; after a month of not getting any shots: he decided to take a shotgun with a slug out opening day of rifle season.
Naturally the buck walked into easy bow range; and he hit it in the chest - with the 12 guage.
He followed the blood trail relentlessly; and when he tired; a friend took over; and then another; for three days the neighbors and he followed the buck; with a blood trail all the way.
But the buck was lost.
That next March he got a phone call from a neighbor- who said he had found the buck.
He went right over to the guys house; and the guy invited him in and walked him over to a telescope- he was a star gazer..
In the scope the buck could be seen bedded down; and after a few cups of coffee and discussion- the deer stood up; and the wound was healed but clear to see.
My uncles hunting buddy shot a deer with a rifle; and then walked up to it and shot it with his .38 pistol. Then he decided to bleed it out and stabbed it in the neck.
It got up and ran off!! They tracked it for miles; and lost the blood trail.
That winter I was ice fishing and talking to a guy that said he had shot a buck that had a knife in its throat....!
It was a handmade knife;and yes; it was the same deer! When the knife owner and the guy that ended up with the knife compared notes; the deer had covered 15 miles in two days before it was killed....
Some days are diamond; some days are stone !!
Congrats on getting your buck. If the water was deep - the deer could have sunk; and then depending on temperature; it could have risen from the gases building up in it.
I have found elk after a good hit in the evening and found them the next day minus all the meat ( thank you bears [not]).
I shot a buck once took the antlers and cape out first. When I came back an hour later; there were a dozen coyotes tearing the rest apart.
Chit happens man.. Congrats on the good shot; and the eventual recovery. He would have been too tough to eat anyway