tedster - 2:09 am on May 25, 2013 (gmt 0)
I'm certain there was some kind of Google Update on May 7. So far, their spokespeople have been silent about it when asked, but it seems clear it was not some kind of "early Penguin" test.
You said your pages have vanished "from the SEs". Does this mean your pages also vanished from Bing? Also, do you have a Google Webmaster Tools account set up?