From the description of the situation, it is almost inconceivable that you have actual significant "burning" of the fiber so as to yield an oxidation state to reduce. It is wholly composed of olefin fibers which have been permanently distorted due to softening/melting and physical extrusion of the fiber from frictional heat and pressure of the part that was in contact with the yarns (because Olefin has such a low melting point, frictional heat and pressure will distort it and leave it set). The sandpaper "trick" will do two things. First it will remove sheen from the flattened fibers, and will render the rest in a more random alignment, attenuating the directional pile alignment the dragging produced.
