If you find someone selling your model as part of his scene without permission, you just have to contact CGT support and they will take care of the illegal seller.
It doesn't matter if you had offered your model for free or for a price.
Nobody has the right to sell or redistribute (offer for free) your model without your permission.
All sellers doing that kind of thing (putting models that they had "found" somewhere on the internet for free in their scenes) are risking being banned from the site.