Phone lost

Not much to do unfortunately.

Mark it as lost and lock it so it cannot be restored and used.

You can also set it to be erasded if it ever comes back online. Do not remove it from your account for any reason.

click here ➜ How to find your lost iPhone or iPad - Apple Support

Beware any messages you get from "Apple" or the "Police" claiming that they have found your iPhone – or asking you to click on a link and enter your Apple ID and password to see its location.

These are not from Apple or the police, but from thieves, fences, and the like who want to clear the Activation Lock on your phone, get into your data on iCloud, etc.

Do's and Don'ts for lost iPhones - Switched Off - Offline - Beware of Phishing – Apple Community

These are the steps you can perform in such a situation:--> If your iPhone, iPad, or iPod touch is lost or stolen,

and/or:--> Use the Find My app to locate a missing device or item,

and/or:--> If Find My is offline or not working

and/or:--> If Find My iPhone or Find My iPad isn't enabled on your missing device

Regards and best of luck.

Giulio