That isn't warping. What happened is that your pads deposited unevenly on the surface of your rotor, and under high heat, the cast iron begins to absorb the material and become cementite, an iron carbide. Since cementite is very hard, it does not wear like a normal rotor, so other parts of your rotors are wearing normally, and the cementite is not wearing much at all. This is why your rotor will not sit flush on a flat surface: One part is worn, the other is cementite.

Rotors do not warp.

- Jim