Please make sure to always have your account synchronized with one of the methods available in game settings - currently Google account for Android devices and Game Center for iOS devices (more available sync methods may be added further).
By synching your game account, you ensure your progress is saved, and protect yourself from loosing important game data.
When your account is first created, it is not synched, so you should go to menu and manually link the account in order to be able to access it later - from another device, after reinstalling the game, etc.
To do so, follow the steps below:
1. Tap menu button in the top right corner of the lobby
2. Tap Settings at the bottom of drop-down list
3. Select the sync method available and connect your accounts