I have no clue how it happened, but I have like 1.5-2" scratch on the exterior of my pano roof. It's just deep enough for my finger nail to slightly catch on it, but only visible depending on the light conditions and viewing angle. I imagine something like this was bound to eventually happen. Anyhow, I'm thinking it can't be remedied without damaging the finish of the surrounding area, but if anyone does have a viable repair solution please let me know.