Ok, I know you are going to want to put me in a rubber room. But what about a critter. Mouse or Chipmonk, something like that. We had a travel trailer a few years ago and one weekend we get to the park and I turn on the propane. Start hearing gas escaping. Follow the hose to an area where some little critter had chewed a hole. Did not cover a big area, but managed to nip the center. The picture looks like mostly "thick scratches" in a generally up and down direction. When I replaced the propane hose the guy told me it happens enough that he was not suprised. Seems like there must be some "smell" that attracts the critter and they chew away. Who knows somebody may have worked on your bike right after lunch of something.
Anyway, don't know but a close look may be able to determine melting rubber (chemical) versus removed rubber (mechanical or dental). Good luck
2009, 900 Vulcan LT Classic
Flashing Tail Light
Wolo Bad Boy Air Horn
Custom GPS Holder