NASA would have to be pretty dumb not to think of that...but then perhaps they're now relying on science contributed during their muslim outreach.
I was just looking at it from that view point. You get an approximate angle of the sun by the shadow of the dwarf planet. The “ice” surface looks perpendicular to the viewer.
A simple refraction would send the reflection off to the right. If the “ice” acts as a polarizing source, and reflects absorbed light to the flat surface, the viewer could see it.