I'm interested to know what it was about these presumably barely-identifiable pair of under-crackers that gave you the confidence to declare them "clearly not mine"?
Men who deal with this kind of stuff seem entirely unaware of how profoundly uninterested anyone else is about the mechanics of plumbing. A fella came round yesterday and insisted on taking me into the basement to point out all of the various pipes and which flats they belong to.
Still, at least he didn't rape me.