In the pilot episode (S01E01) of The Big Bang Theory, Leonard and Sheldon lose their pants while visiting their new neighbor's ex-boyfriend, as can be seen in below for example.
I realize they pissed him off big time, but it wasn't shown.
Is this explained anywhere what exactly they did to the ex-boyfriend and how he managed to take their pants?
My assumption he just grabbed them off by force, but it can be anything else, hence I'm asking here. (e.g. maybe it's explained in later episodes I didn't watch yet)