I had similar case. Once I found my free model as element of paid complex item. I was no harmed. Can say more: that complex model looked good and quality... And I just leaved comment below that complex model (something like...): "Glad to see my free model as the part of your project"... And got the reply to my comment: "It's not your element! I made all parts with MY hands from start to end!!!"... And this reply triggered very very big disgusting. After it I decided to assign price to my ex-free model and reported this case to administration. Administration (all hails and thank them) suspended that complex model. And the same model was deleted from 3dexport after my request... I learned lesson and after all I don't giving models for free anymore (except when I'm giving something as bonus to my customers and buyers).
...and it's one of reasons why I never using free downloaded models as parts of my projects (but sometimes i'm using free models from internet as reference for remodeling or modifying).