20/20 hindsight and Monday morning quarterbacking aside, one of these might be useful for hunting in low light conditions or dense undergrowth.
http://www.aimshot.com/heatseeker.php
Frank Sinatra sang of regrets. I've also had a few.
The good thing about forums and boards, is that those of us sitting at our keyboards can learn from the experiences of others. Thanks, Clayfish, for telling us of your case. Sharing your lesson will allow it be learned by many. Maybe even more than would be reached by the old-timers, some of whom seeem contnet to preach the Gospel, instead of trying to teach the multitudes.
The deer's death was a given ... and according to your recounting, was better than many. Your loss was the vultures, and other scavengers, gain. You sharing let's all of us profit.