My WordPress site reset itself

Hi!

Last night I setup an install of WordPress using cpanel. I then I added a few extra themes, slightly modified one with a new header logo and then posted a bunch of content. When I went to bed everything seemed fine. This morning I noticed all my posts are gone and the theme has been reset to twenty eleven. My user account is still intact, the extra themes I installed are still available and the theme I modified remains intact (it didn’t revert to the original).

Does anyone have any idea what’s going on? I don’t expect to get my posts back but I would like to know what happened before I start again.

Cheers!

Rick