Brother, that was an awesome hunt and write up!
Like you, I've been doing this for a long time...
I'm a firm believer that some critters are just put together a little different than others of the same species....I've seen enough both inside and out to confirm it. Couple that with the fact that some animals just have an incredible will to live and you have the ingredients for what you just experienced!
I know a lot of folks are saying one lung.....but from the photos....even with the angle, that still should have been back of near, and thru the far lung.....
But what it actually hit on that old girl...we'll just never know...
In the end all we can do is try to make the best shot as humanly possible....once the arrow is released...all bets are off.
Great job buddy....look forward to see you and the big guy soon