Well, I've been there too. Three years ago, I shot a buck in a frozen beaver swamp. Knocked him down with one shot and he didn't even kick. Worked the lever on my Marlin 336
(.35 Remington) and the thing jammed. I couldn't clear the jam but sat and watched the deer for ten minutes. Not a twitch. I jacked my climber down the tree and approached the buck. When I was within twenty feet he jumped up and hauled butt as I watched helplessly. I walked over to where he was laying and there was lung tissue and a swatch of hair about six inches in diameter.
I searched the rest of the day in that damned frozen swamp in 16 degree temps. Not a sign.
The jam really ****** me off. Used it as an excuse to buy my Browning BAR in .300 Win Mag.
A tip, though. Met some guys at the range that hunt a few miles from me. They've got a small beagle mix dog that they've trained to trail wounded deer. They don't use the dog to hunt just to find deer. Works really well, a lot better than trying to blood trail in the dark. I'm thinking of doing the same.