Is it stained, or has it simply rubbed the shine off the tank?
Try some of the 3M Finesse-itII(a real fine polish), and see if it will perk it back up. I saw some dull spots under mine the last time it was off also. I thought about using a wire brush to rough up the back side of the bib, so it was more like suede, and less smooth and hard, to see if it'd help. I have waxed the tank alot to try and get/keep a good layer of wax down to protect it. Worse case, if you can't get the shine back, but the paint under the clearcoat is still good, you may find a paint shop that will prep and reshoot the clear(this is only something I've wondered about, not done).