If you did not delete your blog content then it was deleted by someone who had access to your login information.
1. Go to your email program and change the password to a very difficult one because that's how many hackers gain access to email accounts and to blogs.
2. Change the password on your WordPress.com username account to a very difficult one. http://en.support.wordpress.com/passwords/#change-your-password
3. Register a new blog http://en.support.wordpress.com/register-a-blog/ Be sure your blog password to a very difficult one > http://en.support.wordpress.com/passwords/#change-your-password
4. Disable post by email > http://en.support.wordpress.com/post-by-email/
5. Disable post by voice > http://en.support.wordpress.com/post-by-voice/
6. Use a secure, encrypted connection to connect to your Dashboard. Under Users → Personal Settings, check the box that says “Always use HTTPS when visiting administration pages, and click Save Changes.
7. implement two step authentication http://en.support.wordpress.com/security/two-step-authentication/