Sorry to hear your design was stolen. This is one reason why I open-sourced my whole design; The way I see it, a very small number of people are going to steal your ideas no matter what you do.
I think if you tell us how to spot the fakes and share it that information with everyone, most people who know, will support you and buy your real thing.
The decision to open-source or not is the choice of the designer and should be respected. I thought about it along time before I made the decision. There are many reasons, but here is an example -
Someone in CN started manufacturing a much cheaper copy of the diydrone control board. Of course, this is OK if the clone maker follows the rules of share-alike, give-attribution, but in this case they did not.