Q: While highway driving, sunroof exploded outward

We had a very frightening experience. I was driving the car on the interstate at a higher speed when the sunroof exploded! The bang was deafening! Before this happened, the sunroof was closed, all windows were closed and the air conditioning was on. There were no cars near us, so no one threw anything; plus we were not on a bridge. When I took it to the Lexus dealership, I was told that there was not a problem and that something had to have hit the sunroof for it to explode. I asked them why was the remaining glass bowed outward. It would have been bowed into the car if something had hit it. They had no response. They also stated that they didn't see any record of this happening to this make/model. While researching, I have found multiple cases like mine, with my make/model. It might be cheap glass and/or a roof-design flaw. Whatever caused it, it is a Very dangerous problem and there might even be cases where accidents happened due to it and afterwards no one knew that is what caused the accident. So you can see why we are scared to drive our car. In your experience have you heard of this before and can you tell me if there is a fix for this so that we can safely drive our car again?