We had a similar thing happen last year. A friend of mine was out from Vermont and shot a 4X4 (one of three bulls we saw moving across the plains in NW Colorado) with a 7mm Mag at 50 yards. He claims he hit exactly where he was aming, but when we asked where he was aiming, it was too high and too far back. Didn't break the shoulders, didn't hit the heart. Looking at that anatomy pic though, I can't believe he could have missed the lungs.
Anyway, he was aiming better than 2/3 up the body so he missed the heart by a mile. It left a sporadic blood trail so they tracked it for a long time before losing it. A real shame, as I'm sure that kind of hit has to be fatal eventually. He was just sick about it.
I couldn't help track because I was gutting the 5X5 I shot out of the same trio after they ran away from my friend.
It was my first elk hunt, and I decided right then I was moving to Colorado. Eight weeks later my flight landed in DIA.