Explosions in the kiln are terrifying. @patcoleman's right about the big torch making you a believer. What's your full process for flame annealing now? Do you check for bubbles or cracks before firing? I'm curious if there are specific signs to look for that could prevent another disaster.
Actually, I think checking for bubbles and cracks is a waste of time. You can't see the real stress inside the glass. The only safe bet is to just run a full kiln cycle every time, no shortcuts.