Sedan rear windshield defrost line damage

Its not quite yet cold up in the NE (82F) but I just noticed that either the PO or the dealer removed some stickers on the inside of the rear windshield (way at the bottom driver side) and left some residue. I was trying to remove the left over adhesive and noticed that one of the defrost bands looks like it was damaged. It looks like a thin orange string.



My question is there any way I can test if its working properly?



Also if it is damaged, can this be repaired or does the whole rear windshield need to be replaced?