This is an old film camera trick, & I don't know if it would apply to the digicam. Use a big lens hood that keeps sunlight off of that scratch, &, if you can, take the lens apart to use a sharpie pen on the sides of the lens elements. The black sides of the lens element glass will lessen the amount of reflected light bouncing around to eventually hit the film plane, er, sensor. I would not try to buff that scratch out, as it will affect the optics of the lens with unknown results. Just my 2-bits worth.
While a lens hood may work, the whole idea of me having this camera is to have something in a small package without any extraneous things to go with it.
I think this one is just going back to Canon.