Iphone 3gs screen popped out.

This morning I took my Iphone 3GS out of my bag and the screen had popped out from the top. The bottom is still and when I try to press the top back in it will not move and it creates pressure points on the screen. It has not been near water, was not dropped, and has not been out in the cold ( it was even in an incase hard plastic case and the screen pushed itself through the case) Just wondering if anyone else has had this happen...