I was cleaning the windshield on my girlfriends car when I noticed that there appears to be either a chemical stain or etching of some sort on the inside on the windshield...I couldnt get it captured in a pic but whenever the glass is wet it looks like there was a chemical splashed on the windshield and ran down it, I cleaned the glass 4x using invisible glass, glass towels and surgical grade lint free towels I feel a lot of resistance when wiping over it and it looks like it comes off but then I went to do a distilled water wipedown and its still there. Has anyone encountered this before or know of any products that may remove it aside from glass cleaner? Any help is appreciated, thanks in advance.