Yeh, I know if you don’t want it stolen, then don’t upload your models… An online business is selling my models and has the audacity to put in the terms and conditions “All content on XXXXXX Models, including text, images, branding, and design, is protected by copyright and other intellectual property laws. You may not copy or reuse content without written permission”
I think you should have left their name in your post… 
That’s probably more cheek than a proctologist sees in a year… 
Sad that it’s so widespread. Unfortunately you aren’t alone.
Do you have a record of your designs? if makerworld did a false takedown can you still prove ownership?
If not, make one FAST.