Same exact thing happened to my son on a huge rack, 15 yards, steep angle, quartering toward him. He just had the smallest of targets, which he's pretty good at, hit the shoulder bone and the arrow came back clean, broke at the mechanical broadhead screw. The deer ran 25 yards and stopped behind a tree for 10 minutes. No moving around, stood still, then finally took off on a slow, labored trot. My son's still talking to himself about it. He just can't believe it didn't go through. I'm trying to justify it by figuring the angle and the weight of the arrow broke the head at the screw and didn't properly deploy. No blood to speak of, just a little at the impact site, which means he'll live to see another day. We don't usually see deer that big in our area, so it's eating him up. C'est la vie.