I did this A LOT in high school. It was the 90's and everyone wore briefs, or bikini briefs. I wouldn't even wait until they were "discarded" or forgotten, admittedly. I was pretty terrible about it, actually. Our football field was a fairly large distance from the school, so during football games I would go tooling around in both locker rooms. There was one time I stole pretty much all the underwear from the opposing team - something like 20 pairs in all. I also swiped a pair of bikini briefs from one of our hot coaches while I was house sitting for him for the weekend. I've taken a pair of briefs from a hot guy I vaguely know. We were at the local Y, and he left his white briefs on the bench next to his bag. A couple of times I have taken a pair or two of seemingly abandoned underwear, but honestly I prefer to know who they belong to. Either way, it's so, so hot.