I am more surprised that all of these flat glass windows don't break every time we slam the door with the window down, than I am that yours broke. Flat glass has no inherent strength compared to curved glass.
I have a question for you. When the window is rolled down, is the glass excessively sloppy or exceedingly tight? You would have to take of the cardboard panel and/or lower hinge cover to check that. Sometimes the bottom of the wing vent support gets abused/twisted when that nearly-impossible-to-get bolt gets rusted solid and someone ham-hands it to get it loose.
Carl
