My take on it is that if you shoot a firearm at a deer and it reacts then you’ve hit it and must track. I rarely look for hair or blood where the deer was standing because a hit deer will leave plenty of sign, no snow needed. The first thing I look for are the dig marks made where a hit buck takes off. After that there will be scuffed leaves, broken branches, etc etc. You can track a deer a very long way like that if it is hit. Some years ago I had a friend at my camp in NW Ontario. He’s a great guy and an excellent shot, spending much time at the loading bench and range each year working up pet loads. He’s about the only guy I know that could take my rifle after I’ve got a very nice group at 200 yards and duplicate it, not that I’m such a great shot but that he is. He’s deer hunted a lot but almost entirely in an EUP family camp where any buck is usually a rare sight. So he’s sitting on a rock bluff looking down into a swale when a buck that’s in his words “a big buck, a very big buck!” walks outta the swale and he shoots it in the chest with his 7mm short mag at 50 yards. The buck spins around “kinda shaking” so he quarters another shot into its chest and the buck takes off and disappears into the swale. I’m on a rock about 200 yards away and I know it’s him shooting so in a few minutes I radio him and he tells me what happened. I say “that buck is dead within 50 yards, let me know if you need help”. Fifteen minutes later he nervously says “I can’t find any blood or hair” so I tell him “screw the blood and hair, you hit it” and to quit tracking and I head over. Once there I have him tell me again exactly what happened then start tracking, having him follow behind me. It’s tough at first because my friend has walked back and forth in the snow looking for “sign” but about 25 yards out I see where snow has been brushed off a log to the left of the shooting lane. I ask my friend if he’d walked there and when he says no I take a step and then see a heavy dig mark in the snow a bit further ahead. I point this out then see another ahead and a few steps later is spray and there’s his nice 11 point buck. It truly had gone less than 50 yards, no blood for about 40. While later taking my friend to the airport he said “Well, I learned something new this trip: how to track a deer without blood or hair”! I got to repeat the lesson a few years later, but I put him in front and he did find the first broken branch that helped lead us to his buck. I’ve done the same for a number of friends because I learned to track on my own, and as a colorblind guy I quickly learned to look for other signs of a hit deer. They WILL leave sign. So to me a deer that reacts is a hit deer so you don’t need to look for blood or hair at the hit site. I know there are exceptions but they’re rare, so mark where you last saw him and get out there and look for where he’s run. He will show you.