As others have said you are back in the search results having been looking for an answer to a problem that hit me this morning. Almost all my 400 pages have vanished from the search results even though they are still showing as indexed. 95% of terms that were ranking as high as no 3 are no longer showing although one of two terms are still ranking but bit lower. Looked on webmaster tools and can't find an issue so for me unfortunately webmaster tools is not the answer so off to continue my search of the internet for possible answers.