First … I assume you have a backup of your SQL to restore from?
It seems odd that you have lost only one table – why not all the tables in the database?
Not Hacked
htaccess rules corrupt / wp supercache / permalinks??
When you say you can’t login .. is there an error? can you get to the password reset screen? /wp-login.php?action=lostpassword
If you think this might be the case, you could start by renaming the plugin folder to old.plugin this will deactivate them all … then update the .htaccess rules and delete all the WP-SuperCache bits.
Can you restore from a SQL backup?
If you think you’ve not been hacked then maybe you need to restore from a backup of your SQL and see if it needs to be optimised / repaired?
If you can use a tool like Sequel Pro or SQLYog you’ll be able to restore from your backup of your SQL dbase.
So you think you were hacked?
Can you change your FTP / sftp account details immediately 🙂
Then you’ll have to restore from a SQL backup …
Now open wp-config.php and delete all the values in SALT and go here to generate new SALTs This will force all users to re-login
I’m going to guess you have PHPMyAdmin (which always has an account called root) and that you can login to PHPMyAdmin from any IP address? — this might explain how someone got in.
Check and change the password. Ask your ISP to block access to PHPMyAdmin except from your IP and get a static IP if you don’t have one already.
Do you have an WordPress Administrator account called Admin and someone guessed the paswords?
There is one hope … your hosting provider might be able to tell you who logged in to PHPMyAdmin and at what time.