it's happened to me many times.. and on ebay.. where it's really difficult to get everyone to stop using my images because of a million chinese replica retailers under different names LOL.. I gave up after a while.. I just hate it when my stuff is authentic but it's used to sell a replica
but they always stop when you send them a friendly reminder.. I've never had someone not comply.
of course I've never made a dime off my pics and have no interest in that so your feelings and situation may be more acute than mine.