I had always heard that the requirement was that it was an article that you had removed from someone else the night before.
There really ought to be a manual somewhere for this stuff.
Yep, they are supposed to be "trophies"
I could never bring myself to collect any "trophies". I've always been too afread that one night I'd be hanging out in a bar, and hear, "Thats the sicko that stole my panties!" "No, no, they were for the panty tree, I SWEAR"