"sudo service vsftpd" returns "Unknown job: vsftpd"

I had a similar problem and discovered that it's caused by an environment variable. When you use su, it leaves the UPSTART_SESSION environment variable set (from the original user's environment), which breaks things. Using sudo or su - unsets it, so any of these will work:

$ sudo service vsftpd restart

$ sudo su
# service vsftpd restart

$ su -
# service vsftpd restart

$ su
# unset UPSTART_SESSION
# service vsftpd restart

Try with sudo, it seems a bug or that you don't have permissions over service with root.

$ sudo service vsftpd status

should work, indeed is working now for me in front of my eyes.