Hi Stumbler! Nurse Joy here to assist you with any Account related FAQs 📒  
To recover your lost progress on iOS, you need to have your account connected to your Game Center or Facebook profile.   
To connect your account with one of these platforms just open the Game, go to "Settings" (top right), then choose the platform you wish to bind your progress with (Game Center or Facebook), tap "Login", then follow the steps to login and complete the connection.
After that, you can follow the same steps to load your account on any other iOS device. Just make sure you're using the same Game Center or Facebook account that your game account was connected with. Using Facebook will allow you transfer your progress to Android devices as well.
Please keep in mind that you cannot use Game Center or Facebook to load your progress on PC (using Steam).
If your account progress got lost and it was not bound with any of the platforms mentioned above, please send a message to our Customer Support team and we'll do our best to assist you. You can contact us by using the chat widget on the bottom right of our Support Web Page!
Always a joy to help!