No. My finished render is no more derivative of the prop than my painting is a derivative of the paint. Nor is there actually any binding agreement that I have with the prop maker any more than I have a contract with the company that makes my paints, just by the fact of my using them. A lot of people would like it to be so, but it's untested whether it would really wash in court. In any case, in the example I gave, there is certainly no agreement between the boss person and the prop maker, and I am no way responsible for what boss person does.