John, that's the crazy thing about bullets that I don't think we'll ever solve. You mention heart & lungs destroyed plus the off shoulder, so that bullet had to work extremely well, yet the animal runs off. That could just be that animals will to live, and the next animal drops on the spot from less performance, it happens & we can't explain it.
But I don't know if we can blame that on the bullet if it does everything you just described, I've seen the same thing but can't explain it either. It's the biggest X factor in hunting & probably always will be because of angles, impact, velocity, etc. just such a crazy mix of events once that bullet leaves the barrel & yet fascinating with the end result.
Just like the 357 Gold Dot at 1400 fps with no expansion, that bullet at that speed should give some expansion on a Potato!

Dick