Had the same exact thing happen yesterday evening. I shot an average size doe with a 165gr .30-06 through the rib cage, lungs turned to mush, totally destorying one shoulder on exit. It was not an easy shot due to the angle and distance (100 yds quartering away in thich brush) and based on how she took off, I was sure I had missed.......until I heard her pile up. No way an animal should be able to run 100 yds with those injuries, but she did. It happens. Next time you might hit one exactly the same way with the same load and it could die in place. Go figure.