Like the man said, you get to hunt him again!

Where was the obstruction to your line of sight? I'm wondering if the arc of the arrow could have made a lung shot possible.

But 72#'s at 31 inches! If you were sure you could hit the center half of the neck - is that not a sure kill? Either break the spine or sever the big neck arteries. I'm not nearly that good a shot, especially out of a tree (not that Id ever be up one, except for the figurative kind) but you might be.