I'm glad the issue was resolved to your satisfaction.

As a Graphic Designer/Illustrator with an online portfolio I run into this problem quite a bit. Most of the time it's resolved without much hassle, but there have been a few occasions where it ha caused me a great amount of trouble and anguish.

About 50% of the time, as you had happen, I've had problems with one person taking the material I created to give it to a third party who may not have known it was stolen. In those cases I just inform the person of the infraction and let it go as long as they're not making money on my work. I will also tell them they must immediately stop using my work unless they purchase the rights and give proper credit.

The other cases have been willful theft, and in these instances it can get quite nasty.

I've also been the third party who was given someone else's work to incorporate into a project. It's usually pretty obvious when it happens, and when I am aware I will inform the person that I can't legally do what they want unless they purchase the rights to the Photo, artwork, illustration or otherwise get permission.