I still see recurrences of these in my WMT tools:
Each time they've shown up; their date stamp is one day after my drop. It has the 19th on it right now. I dropped on the 18th. While the thing is properly 404'd on my site; that it has now happened twice is more than a coincidence.
It could be that lots of "low quality" links (such as these) damage a site temporarily, inducing a "6th position penalty" - which one of my sites has been affected as well - inner page. Home page moved from 4 to 11. The one that dropped to 6th was at #2. So its not a -5 drop. The effect is varied. This particular site has never dropped in Google rankings for years and years.