Erm, looks like all the posts are actually there on the site still, they just included a post and their pic and text to it.
The database should be fine if a backup is made likely.
You might be able to delete everything, format the site, and re-upload the database (with their post removed) and it should be back to normal possibly.
Yeah if this is an SQL injection hack (Which I suspect) any any posts are appearing as deleted.. trust me.. they are in there.
I had a few older PHPNuke sites hit with this till I locked them down and good.
Agreed - looks like the site data is still there...Seems almost like they changed the header.php and index.php files in the theme (which should be in /wp-content/themes/yourtheme/.