NOT the world's worst deer hunter... you found hair so sure sounds like you hit it. World's worst would have flat-out missed it.
In all the years I've hunted, I've only had 3 deer fall in their tracks. Majority have run, and run HARD for some distance. Incredibly, even though they were fatally wounded and likely lived less than a minute or two, they managed to sprint between 50 to 200 yards to the very toughest spots to recover them such as THICK bramble thickets, swamp bottoms, etc. More than one either bled VERY little at the initial shot site OR had blood completely stop after a few yards of their run.
Shooting them in the evenings makes recovery a FAR bigger challenge than in the daylight of early morning. Don't give up hope you made a lethal shot. If you can, get back out at first light so you can look for blood and / or do a patterned walk search that covers AT LEAST a few hundred yards distance from your shot site.
If you've followed some similar old posts, you'll know you're in GOOD company with MANY on this forum who've had tough searches for deer we've believed should have dropped. Hope that brings at least a bit of comfort. Will keep fingers crossed you have more luck than it sounds like you think you may.