Try using Google's image search function. Of course, if someone changed the filename, that isn't going to help :-) If you use Digimarc to digitally watermark your images and subscribe to their service they have a spiders that crawl the web and locate any marked images, supplying you with a report of where they were found. "eventually you will get caught" - Er, no, not unless you plan to go to everyone's home and look on their computers.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken