Joe, Congratulation on the nice buck!
Way to follow up after the shot and stick with it. Thanks for posting; hopefully others can learn from your experience to take their time when following up their shots. It is my belief that most unrecovered animals are a result of the bowhunter following up after the shot too soon.
John’s theory of the pinched/severed spinal nerves makes sense and could explain what happened to a cow elk I shot in 1993. I hit the elk high in the spine with a broadhead and it walked away like nothing had happened. Thinking it was a minor wound and the elk would be fine I gave it four hours before following up on the shot and busted it out of its bed seventy five yards from where it was hit. It staggered out of its bed, crossed the Gallatin River (out of the hunting unit), and into a stand of pine trees. We figured it was in bad shape and backed back out for another three hours before resuming the trail. Because the elk was out of the late season hunting unit we had to leave our bows on the other side of the river and pursue the elk without them, hoping it was dead, or if not dead hope we could herd it back to the other side of the river for a finishing arrow. The elk was about fifty yards into the trees, and like your deer, it was unable to get up and run but could lift its head and watch us. Brother Bob went back to the car, got his lasso, returned, lassoed the elk, and then finished the elk with his knife while our friend Roy kept it distracted. (Note: I wasn’t in on the final part of the kill as I had started tracking another friend’s elk after we busted mine out of its bed.) The elk was about gone by the time Brother Bob finished it. Until reading John’s thoughts regarding pinched nerves I hadn't figured out why we were able to recover the elk because its spinal cord hadn’t been cut.
One other thought, if you are having trouble reaching full draw, I recommend trying a clicker.