I don't even know how to contact the Google search people...
The best / only way to do it is to start a thread in the google webmaster tools forum (if you haven't done so already).
I would name the thread something like: Scraped Content Ranking #1 - My site dropped to #XYZ
I would give as many specifics as possible.
You would most likely have to include the link to your site and the link to their site as well to get any sort of meaningful advice. Note that even then, you might not have a google employee comment on your site or that of the scraper.
Also, there is another thread on this forum by an alorentz (I think that is the poster's handle), where he had experienced something similar. However, this happened to him in November. It might be a good idea to contact him and see if he has any suggestions.