WordPress dissappeared

This morning I was writing a post,uploaded an image for the post (.jpg) and clicked save : got this message:

It doesn’t look like you’ve installed WP yet. Try running install.php.

The install.php had a link to it which if clicked would run the WP again.

Horror of horrors: the above message with the link to install WP again was available to see for all visitors to my blog site.

Though the host admin is looking into the problem, I’m not sure what happened. Anyone faced any similar problem?