Well, you can usually contact people via their ask box. This is theirs:
electric-sympathy.tumblr.com/a…If they don't follow your request to list you/delete the photo, you can report it by going here:
www.tumblr.com/helpType "copyright" in the search box at the top, and the first thing that will come up will be details for an e-mail you can send about your work being stolen. It's not the easiest way to report things (they really need a form/report system), but people have told me it works pretty well.