Thanks for the replies. The mask I was thinking of using is one that just goes around the eyes (ala The Incredibles). Me, personally, am terrible at noting details and would make for a very unreliable witness, but I'm sure others are much better at identifying people they've met. Although, a mask could be used to hide a blemish, scar, or other noteworthy facial feature.
I like the small-mask look for the character, and I'll just have to ignore my logical side for the sake of art.