Tracy, thanks for writing this.
Design plagiarism is a very big problem and has been for a longtime — although usually more disguised in comparison to the example that you suffered from. I watched my fellow design students do nothing but rip off existing work while in school and have watched some of the most blatant offenders become the most successful in their careers due to the lack of true design management/oversight in most companies.
Personally, this past year I had a branding project of mine plagiarized by an actual agency in Mexico. My original creative was stollen from Behance and can be seen here:
And while I probably could sue the agency, I have neither the time nor resources to do so.
Unfortunately, with the internet the ability to steal existing work has become super easy. Fortunately, with the same internet the ability to catch such offenders has also become easier.