Where I grew up I had this happen to almost every car I owned at least once. Such a feeling of violation. I had my front windows tagged while I was sitting on the couch just the other side of them. Still no idea how I didn't hear it. Locks popped on garage and cars, car windows shattered, etc. I learned how they did it without making noise. A broken spark plug snapped against glass will create crack, then just a couple more Spider webbs and then push in... completely silent. Our so a cop told me.
Sucks man, sorry to hear it. Good thing you don't keep a gun in the car.