I'm sorry to hear what's happened. But unfortunately there's no LW support phone number. AFAIK there's no way of finding out how many people may have downloaded sensitive files, apart from searching for some of the file names & seeing if they show up in your search results.
Even then, a search won't be 100% accurate, as it's not possible to search the whole Gnutella network at once. Also, a search will only show results from users online at the time. There's no central server, files are shared by other users.