hmmm, the way I was taught to change a tube involved a step that makes sure the tube and tire are properly seated...hard to describe-better seen.

The earlier sound and blowout don't go together, a sound would indicate a slow leak-which she likely would have felt over a few miles, a blowout like that is very sudden-no warning noise/signs. I had one recently, there was a nice big hole in my tire which the tube blew through-at the time I was doing 20, 2 feet from a logging truck doing 50-that was scary, not a fan of blowouts!

The length of the split is also odd, any chance there's a rim tape issue (or lack thereof)?