Is this Oleophobic screen wearing off?

Well, it's been about ninth month since I bought this iPad Air 2, and I noticed when you turn off the screen,

there is a little of a.. Scar..

I was not sure what it was, so I rubbed it with my fingernails and could definitely notice it, but it's actually quite impossible to notice it directly on the screen with the screen turned on. Only on the edges you can see very very minor color diffraction. It is clear, it has no other symptoms.

It just feels like, I rubbed off or something of very thin layer or coating of something on the very top layer of the screen.

What could this possibly be? I still have my warranty valid, considering it lasts a year. Few months to go.