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It would sound to me that your shot was low forward and got front shoulder. That will give you your white hair, good blood trail and not fatal. Well not fatal right off anyways some will live and some get infections in wounds and ultimately die. And can still get around but with a bad limp but in spooked they would still be able to run with very little tell tell of injury.
It's something all of us bow hunters go through, deer are amazingly fast on a drop, tuck, turn on the sound of a bow shot. I've shot deer broad side that turns so fast the arrow came out center front chest. Have had them drop and arrow what would had been a perfect heart shot got right over their back.