My first whitetail buck with bow was nearly lost due to lack of reaction and no blood trail.
He came walking in on a well used trail and stopped for a moment perfect broadside at 20 yards. I let the arrow fly and would have sworn I watched it hit 10-ring for double lung and top of heart. The buck continued his walk on down the trail and then I watched him stop at the edge of the timber under an evergreen pine for a couple minutes and figured he would go down there. But after a couple minutes of hanging out sniffing the air and ground, acting completely unphased, he continued on and out of sight like nothing happened. Meanwhile I'm in my stand dumbfounded at the lack of reaction and wondering what was happening.
When I got out of the stand and went to my arrow, it was full red from tip to nock. But there was not a drop of blood anywhere. I followed the trail he walked to the location he stopped. Nothing. Not along the trail, not where he stopped, no sign beyond in a few passes of the direction he headed. I went back to the starting point (arrow) and did it again. Still nothing. Other than the red arrow, there was zero indicators of a hit. But the arrow told me it was a for sure hit, and I still felt like I'd watched the arrow hit exactly where I wanted it to go. It was full dark by this time, so I decided to come back the next morning. I did the same search again from hit point to where he stood with still no blood found. I decided to walk the trail further just to see if I could find blood further on, and just about 30 yards further and around a bend, I found him laying dead.
Coyotes had already found him overnight, so I couldn't evaluate the insides, but the broadhead holes through both sides of hide and rib cage said it was a perfect shot, just where I thought it had hit. I can't explain how there was no blood or no reaction, but it definitely speaks to sometimes weird things happen. Without the arrow, it could have easily been called a miss.
This occurred on our own land, so it doesn't necessarily apply to the question of this thread, but had it been a guided hunt, the red arrow would have been the proof of a hit. Then it's up to us hunters (and/or guides, PH's, Trackers, etc.) to take the necessary steps for recovery as best we can. I lost the meat to coyotes, but gained a story and lesson. The cape was just long enough to salvage for a shoulder mount (coyotes tore up the back end), and the taxidermist did a good job of repair and skill to fix the nose.