In over 50 years, 40 of them traipsing around hunting or where others hunt, I found 1 deer that was illegally shot--from the road, and not a legal buck during a season when only bucks are legal. I heard the shot--which had to have been from within feet of the road if not from the vehicle--watched 2 people walk into the treeline, and then a few min later walk back to car. Didnt think anything of it until the next day when I stumbled onto the dead deer and realized what I'd seen. Called game warden, but that's all I could do at that point. Thats not the same as an unrecovered deer, that's just blatant poaching and then walking away becasue they couldnt pass it off as a legally taken animal. I have never found a unrecovered dead deer that I could say with any liklihood was shot by a hunter, as opposed to just winter or coyote kill. And I have found 2 deer carcasses that had a very small amount of meat taken (backstraps only, etc) and the rest dumped in a ditch--not sure if those were poached or just a really poor home butchering job as the deer could conceivably have been legally shot.
My dogs have found many unrecovered dead or wounded pheasants. And I have found clearly shot/left there bobcats and coyotes.
I would say around me finding an unrecovered hunter-shot deer is extremely rare. I suspect many of the shot unrecovered deer are not in places where they'd likely be found any time soon, but I suspect there just arent enough deer and people hunting them for it to be widespread enough to really register.