In the case you should experience account loss, do not panic!
First of all, check if you were connected to Facebook or Google Play Games. If so, your account may be retrievable by just reconnecting to the respective service with the same account that was used before.
If you forgot to sync your progress either with Facebook or Google Play Games, do not hesitate to contact us via e-mail: firstname.lastname@example.org
Do not forget to attach your User ID.