Thanks for that photo. It looks like the bullet went not only through bone on both shoulders but also the heaviest part of the spine--which is some of the thickest bone on deer (and elk, etc.)
I am not making "excuses" for the bullet, but just noting you never know what might happen when you pull the trigger. One of the oddest bullet recoveries that I have personally witnessed was a 340-grain .416 Woodleigh Weldcore bullet from a wildcat round. Muzzle velocity was around 2400 fps, and the animal was a female fallow deer around 100 pounds live-weight, which was angling not quite directly away at around 100 yards. At the shot the deer staggered around 25-30 yards and fell dead.
The bullet angled from the rear right ribs to inside the left shoulder. The base was found protruding through the skin, after the expanded bullet tumbled and the "petals" hung up on the skin. It retained around the typical 90% of its weight.
