If your mobile device is lost or stolen you can delete a device at any time by logging onto your account from a PC or another device and navigating to Profile > Service Center > Manage Fingerprint/Face ID > Fingerprint/Face ID Devices. You can delete the lost/ stolen device from the list of devices currently authorized. In addition, anytime a new fingerprint is added to the device, re-enrollment is required. So a lost device should not be able to access your account without your fingerprint or account Login ID/ Password.