barcode in window?

[Kooldino]

Whenever it gets cold or frosty, I notice that my driver's side backseat window has a bar code looking outline in the frost. It appears as if it's in the middle of the window. Anyone else notice this?

 

[C Rae]

YES, BUT AFTER CLEANING THE CLASS 2X IT'S GONE. FACTORY THING

 

[Kooldino]

so WHAT is it? I've cleaned the glass before...