Unfortunately if you have no backups or did not upgrade for automatic backups -- there is nothing to restore from.
I hope you immediately changed all your passwords to prevent ongoing problems. I know this is not what you want to hear but it is a lesson many learn the hard way. Now that you have experienced this you'll make sure to get a backup process in place when you rebuild your site.
Judith "I find that the harder I work, the more luck I seem to have." ~ Thomas Jefferson