Volkswagen Shattered EOS sunroof Houston, Nationwide

I have a 2008 VW EOS that is a hard top convertible and also a sunroof. I have had it since May of 2011. I bought it certified pre owned from the Momentum VW dealership. I was driving on I-10 Friday evening around 8pm when my sunroof exploded and shattered on me. I didnt not feel any rocks nor were there any cars next to me. I pulled over while trying to protect my face and exited the freeway. I pulled into a lit parking lot and took pictures of my car and called my boyfriend. My windows and windshield were intact. I did not see any external damage to the body of the car. He had me search the car for any rocks, bullets, or stones. I didnt find anything.
I had glass in my hair, on my body and a few cuts, but I was able to drive home. I called the dealership the next day to inform them of what happened. They explained that there wasnt much they could do. I called Volkswagen of America on Monday. They gave me a case number and assured me someone would look into it. I was then called by the dealership on Tuesday to be informed that my case was closed and that VW had no way to prove what caused the glass explosion. I was repeatedly told that VW could not take responsibility for the incident because they could not prove that it was not caused by an outside influence. I am not unreasonable, but I would like them to investigate what type of influence would shatter a sunroof. If I get my car fixed, I am afraid to drive it. They keep telling me that this foesnt happen. It happened to me. I have no idea if this will happen again