If you have lost or misplaced your phone, and have thus lost access to your Google Authenticator key, there is no need to worry. There is a way to restore your Google Authenticator key to your new phone.
First, you will need to uninstall the Google Authenticator app from your old phone. Once the app is uninstalled, open the Google Authenticator app on your new phone and tap “Begin setup.”
Next, select “Scan a barcode” and use your new phone’s camera to scan the QR code displayed on your computer screen. Once the QR code is scanned, your Google Authenticator key will be restored on your new phone.