I have lost two deer in my life and I am willing to my that they were my fault.
The first deer was at 20 yards broadside. I put the pin on him, squeezed the trigger of my release and sent an arrow flying. The shot was high and far back. It was entirley my error. I didn't put the arrow where it was supposed to go. P.S. That was a Easton GameGetter II xx75 tipped with a 100 grain N.A.P. Thunderhead and I didn't get a pass through.
The second deer was my fault. A bunch of doe came out and I picked out the biggest one. There was a smaller does standing in front of her, but her head was covering the larger does butt. I drew back and shot and the small doe ran. My arrow smacked her right in the lower part of her neck. I shouldn't have taken the shot at the big doe when there was a chance that the smaller doe would run in the way. I didn't think of it at the time, but I should have. I tracked that deer well over a mile before finally seeing it feeding along the edge of the woods. I left it at that and later that year she was killed by a rifle hunter.
The thing about my two experiences is that I am willing to admit my fault. You have to trust me on this, but you will loose less and less deer if you are willing to admit your fault in this situation. The first deer I lost, I didn't want to admit that it was my fault. It just made me look bad, but that doesn't matter.
Blaming a b-head will get you nowhere. Mechanicals are proven to be good if you put the arrow where it is suppose to. These horror stories about mechanicals start from posts like this. People will blame that b-head no matter what happens. If it was a Muzzy or Montec G5 that you did the same thing with, you would be blamming that.
Face it, you lost the deer because of human error. Now, I am not saying that I am perfect, nore am I saying that anyone else is perfect, what I am saying is that you have to be willing to admit your fault.
As far as choice of shot, I personally wouldn't have taken it. I can hit 5" circles out to 50 yards with my bow and the farthest shot I have taken was 65 yards (at a target) and I hit that 3-D deer in the lungs. Now, I will NEVER take one of these shots in the field because there are just too many things that can go wrong. Like others have pointed out, a 35 yard shot on a deer is rough even on un-pressured deer. Deer can react very quickly and that leaves a big margin for error. Now, throw into that the fact that deer have been chased around since Sept. or Oct. and they are constantly on alert. This makes they very skittish and they will react to anything much faster. The low-light poses another problem like others have mentioned.... small branches. At 35 yards in the last minutes of shooting light, you won't be able to see a twig, and that is all it takes to throw an arrow off.
This year, I got what most would consider a "perfect shot". I was only about 14 feet up in a tree and I had a doe come in. She stopped at 15 yards but she was VERY slightly quartering towards me. I didn't want to risk anything, so I passed up that shot. Then she worked her way in to about 4 yards broadside and stopped. There was a TINY twig that was covering her vitals. One tiny branch that I could have shot past no problem, but I passed it up. Well, she went behind me into a dried up creek bed that was entirely open. She stopped slightly quartering away at 7 yards and I knew that it was the shot I was looking for. I very softly grunted and she stopped. She wasn't nervous and it was 8:00 in the morning so I took the shot. The result...... well.......
All I can tell you is take the bumps from these guys. They will help you out in the long run. It may tick you off right now, but seriously take it to heart and it will help you out. how do I know...... ask any guy on here about me posting about the two deer that I have lost! The comments that these guys have given you looks like compliments compared to what I got! I have been there and done that, and I took my bumps, got up, and improved myself, and that is all that matters!!!!!