I was helping a guy at work with his bow this year who wanted to try bowhunting for the first time. I walked him through the entire process and practiced with him everyday. When season opened, I neglected to verify my broadheads from treestand height and had the same result as you, missed at 15 yards - nice 8 point. I took the lesson in stride (upset at first) went home and didn't hunt again until final adjustments were made, and downed a doe the very next time in the woods.