I have a 100L Macro which I believe has the same nano coating, not long after I got it I noticed a "blemish" in the coating, it wasn't there when I got the lens. I tried to rub it off but it wouldn't budge, indeed it looked like a pocket of air, or bubble in the coating, certainly it looked to have the third dimension or depth to the blemish. I was disappointed but was determined to either clean it off or get a new front element. With that attitude I set about really laying into "cleaning" it, basically I rubbed the sh-t out of it and did nothing but make many rub marks around the blemish. I was resigned to a new element. However before I sent it off I had my cleaning fluid out and tried one last time, voila, not only did the blemish disappear completely but also the "cleaning" marks all went as well.
Now I recount this not to make myself look like the dufus I was, but to point out that even when we are "certain" the coating is damaged, it might well not be, and further, I find it practically impossible to believe you could rub those nano coatings hard enough by hand to damage them, I know how stupidly hard I "cleaned" mine with zero ill effects.