As a graphic designer, what should you do if you find your work in someone else's portfolio?

I was an art director at a company where I designed and produced a very distinctive jewelry catalog. 5 years later, I find the piece being showcased on the portfolio site of a Jr. that was working under me at the time. I’ve called and emailed demanding the piece be removed from his portfolio site to no avail. I’ve exposed his misdeed to my friends in the industry to try and stop him from being hired should he try to get a job in companies they’re working at based on his current portfolio. However, the work still resides on his site. I don’t know what else I can do.