Your gameplay progress, including your credits balance, is tied to your device. If you perform a factory reset on your device, or if you upgrade to a new device, you will start again as a new player upon installing the app.
If you ever contacted our Customer Support team from the old device, we may be able to assist by looking up your original player data in your help request history.
In fact, why not contact our Customer Support team just to say hi? It will create a record of your current player ID in our system, just in case you wind up having to replace your mobile device at some point.