I'm often amazed how little sign of a hit there is at the site.
Earlier this year I shot a sika hind in the snow. I knew she was hit because I saw her run and it looked like she had a broken front leg, in truth when I found her she had two broken shoulders. However at the site of the hit there was very little sign of an impact and nothing that could have been seen without the help of the snow. On the snow there were a few, and I mean a very few, single grey hairs but on, say, heather there is no way on earth I'd have seen them, especially not with the light going. I could also see the slots in the snow and there was evidence that she'd taken a rather heavy step sideways which, I presume, was as a result of the bullet impact. Had the bullet not have gone through both shoulders or had there not of been snow on the ground there would have been no evidence of this "jump to the left" and I also had doubts that it was certain evidence of a hit; maybe it was just a jump from the surprise of hearing a big bang.
The first blood was maybe 10 yards from the site of the impact and was where her chest had hit the top of one of those big clumps of purple moor grass that had snow on top of it. I suspect the reason she hit the top of this was because both shoulders were broken and so she wasn't exactly running well but, again, a very small change in circumstances could have had her clearing this clump and so there would have been no sign of blood, even with the snow, at all.
The hind got under a small "christmas tree" type spruce about 30 yards from the site of the hit before she died and even with the clear trail in the snow I went past her several times before I dug around and looked under the low branches. Had it not of been for the snow I would certain have walked past her believing that I'd searched the area and that she must have been further on.
Under normal circumstances, with no snow, I can see how even the most responsible stalker who carried out a thorough follow up but who missed seeing the deer run with a damaged leg could easily have concluded that he had missed, and I can also see how without the snow I might never have found her even knowing that she was hit. Given that I found it a useful lesson and I would also be reluctant to point the finger at someone else unless I was actually there and witnessed that their follow up was lacking in some way. Even a tiny change in circumstances can turn an obvious "clue" into something the stalker simply can't see.