Passwords

So yahoo has a new authentication system where it sends you a password to your device.  This seems to be less secure than 2-factor authentication, however it certainly is a lot less of a hassle than having to make and change your password.  The main issue is of course losing your phone.  So, I guess it will be a good idea to keep a strong password on your phone.  Main concern is how does yahoo confirm your identity if you loose your phone and want to change to a different phone?