On the 19th of May our site was ranked 7th on Bing for a particular keyphrase (this keyphrase happens to be a part of the url of our site) Today it was gone, totally and utterly. I gave up searching after page 27. Even searching for its url did not show our site at all. Our site had not changed since the 19th and we had not submitted a sitemap update to Bing or anything else to it. Doing a site: search returns the site so that is not an issue.
Even some of our other sites that have nothing to do with this keyphrase are showing up on pages in the 20's so I have no clue why this main site is not there.
A site I am working on completely disappeared in April and May. Look at the SERP's now we starting come back.
The site had a about 40 top 10 positions. Only a few were competitive though. I have looked across some other verticals and I'm not seeing anything. Therefore an isolated incident which happened over two months?