Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
It sounds like someone hacked your Google account and used Android Device Manager to wipe your Phone. Is it possible that you have given your gmail password to anyone?
And in any case change your Google password immediately, just in case.

Enabling/using 2-step verification is a good idea too![]()
Indeed it is - except it uses the phone as part of the verification which makes it less useful in the case of a stolen phone. But I use it anyway; I enabled it when I changed passwords after the recent(ish) heartbleed concerns.
You can also make some backup codes as well, which is a table of 10 one time numbers that you can print out and keep in your wallet or something, in case you don't have your phone.