Utilize Apple's "Find My" app or website to put your device in Lost Mode immediately.
Use the "Find My" app to locate your device's last known location.
Contact your mobile carrier to report the loss of your iPhone.
Protect your personal data by changing your Apple ID password.
If your iPhone was stolen, file a report with the police.
If you're unable to recover your device or suspect it has been stolen, remotely erase all data on your iPhone using the "Find My" app.
Reach out to Apple Support for further assistance and guidance.