Two weeks ago I was working overnight with my 2010 Raptor outside in the parking lot. We had some rain early in the night then the temperature dropped below freezing and in the morning when I got off work, there was a coating of ice on my Raptor. I started the rear window heat, and when the ice had melted I noticed the right portion of my rear window was broken (glazed). I suspected vandalism, but the glass company man that replaced the window said there was no point of impact on the window. What could have caused it? Can the stress from ice on glass being suddenly heated cause the glass to break?