Oooh, fun! I don't have a story, but I have a couple of prompts...
Season 2 Lois finds an engagement ring (yes, stretch as to "clothing" - LOIS: Not if that's all I wear when Clark gets home.)
Amnesiac Lois finds some of her underwear, knowing (or not knowing?) it's hers.
Season 1 (or Season 2 - Mayson) Lois finds Superman's groupy-stash (remember that scene from Season 4 when they found panties in the Superman mail?). Yes, it's not exactly "one" item of clothing, but still counts. Or it's just the one that got away.
Michael