This has happened to me many times. If somebody steals something I've written and reposts it under their own byline, I send them a scary Cease and Desist email demanding that they take it down within 24 hours or I will "take all appropriate legal action." Sometimes that works. Other times it doesn't. Another thing that can work is to post the email address/twitter handle of the errant writer/publication on your Facebook page and encourage your friends and followers to contact the culprit, being as creative as they want to be in encouraging them to remove the stolen story. That can work too. But you've already discovered the best approach -- write an essay about it!