Describe the hair a bit more. Does it look like the hair was from all over his body from thrashing? clumps? The hair can tell you a lot more by its length and thickness. Just compare the hair to the hair you find on the body of other deer you've harvested before.
That usually applies more to clumps you find because clumps are generally from the shot, whereas hair all over is usually from thrashing and doesn't tell you as much.
Did you see the initial impact very well? A spine-shocked animal will usually stiffen right away before falling and then the kicking or struggling will begin.