The thought of them scamming me crossed my mind. But apparently this particular type of fake 10 has been passing around for awhile; I just hadn't heard of it.

And sure, some people interfere in fights between people of any gender--but just see BruceStein's answer above; gender plays a role in how people think about these things.

However, as for the 'they scammed me' theory, it wouldn't have done the owner any good to have his guy press the matter after I gave back the cigs and took the fake money. So...I kinda discount that theory.