First of all -- awesome bag, my friend has that, and I almost went for it but I'm too small for such a big bag. I got the Bleecker woven pocket hobo instead (similar in style)....
I believe that bag is made of Nappa leather and Coach cleaners and moisturizers are not recommended anyway...this leather is more oily than others, so I would rub the mark with your fingers, it certainly won't hurt. They recommend that for the specialty leather...the oil from the skin works with the leather to fade marks.
I bet if will fade/blend in over time. If you know a good cobbler/leather guru they can probably give you some advice. I'd be worried that if you tried to dye or stain it that it may become more prominent over time.
It's on the back of the purse, right? Heck, if I were you, nothing short of the "f-bomb" on an Elisa would keep me from carrying her!