Then I decided to search an old picture from flickr on a whim and lo-and-behold, I stumble upon it being used in an Irish architectural blog, without any attribution. That blog does attribute other pictures to some studio, but my picture has no attribution.
I had posted it on flickr many years ago with a Attribution-Noncommercial-ShareAlike license.
Here is a snapshot of both on same screen.
|Leaf imprint in concrete, near Deike building, Penn State Main Campus.|
They have used it for 3 years without any attribution! What can I do now?