Well, you have a pretty darn good record if that is the only deer you have lost in all those years! That would be good even with a gun and no archery! There is a "zone" just behind the shoulders ahead of the lungs and high on the back but below the spine that seems to have no critical vitals.
I think I found it. I just make my shot count and if it is by no means a less than 50% chance of not being lethal, I pass it up. That means keeping my shot inside MY kill zone, and not what others CLAIM they can do it at. I hunt mainly with single shot weapons, pistol, bow and muzzleloader. So it makes me pick my shots.