Okay, I have a similar problem but more recent. I have various "mainstream" sites that in November were de-indexed in Google but not "de-listed" ie. if you google "domain.com" it is there, but all the listings are gone.
Yahoo kept them and so did MSN.
Was getting many hits from google.com and many international versions of google and boom gone!
Any ideas anyone and yes I'll post domain names, here is one of them
http://www.CollectorStamps.com