If you were not in the game for a while but see new battles added to your statistics, that is your sign.
How do you tell if your account is hacked? Go to, and enter your in-game name to pull-up your game progress/stats. How this happens is beyond me, but the good news is that you can get your account back pretty easily. Your account got 'hacked.' What this means is that somebody setup the google authentication using their account to block YOU from accessing your account.
