I wondered what that spot was on the side of my phone....yeah, I have the same case and the same smudge like spot on the side. You can tell them you aren't the only one if you like.
Personally I can live with it. I tend to use my phones to their full potential, at work and play, so for me a smudge like that blends in with all the other sh*t that happens along the way.
[EDIT] BTW....good catch.
Dave