For many mobile games,you can login game through facebook account,if you choose this login mothed,when others log the account in unusual areas,facebook system will ask security code or you need to approvel login,if you dont do it,they can not login the account.
If you login game through facebook accounts,for deliver order ealier,you can leave recovery code to seller when you place orders.
you can know how to create facebook recovery code like below:
https://www.facebook.com/help/148104135383285
Remember create new recovery code when all codes are used!because per code can just been used one time.