After reading and re-reading your post, I am assuming the buck was facing left. They way you described it, it sounds to me as though your POI was more left than you wanted, the arrow hit the shoulder, deflected left cutting the brisket which would account for the black hair. What I believe you now have on the property is a deer that should survive provided the wound does not get infected. Also, depending on where the shoulder was hit, he may or may not have use of his leg.
I am a firm believer that if I do not see the animal fall, I wait a min of 15 mins, go to where the animal was standing when I shot and try to determine a hit or miss either by locating my arrow or any sign of blood. If a hit is confirmed and no 'gut' smell on the arrow, I wait a minimum of another hour. If the arrow does smell a bit gutty, I will wait a minimum of 4 hours before taking up the track. Thank goodness that I have yet to gut shoot a deer. But sooner or later it may happen and I will go take a nap or whatever to pass the time.