Why would urls submitted in google webmaster tools drop to 0? It's a small site, only like 20 pages, I submitted the xml sitemap and for about a week it said 20 urls submitted. A day or so ago it indexed about 17 of the pages, but today when looking it not only says that 0 are indexed but also 0 have been submitted.

I did a site search on google and found clearly that pages are indexed, is this just an error on google webmaster tools? Any help or thoughts would be appreciated. Thanks!