lost iphone x

To locate your iPhone in the Find My [Device] app, you must have activated the Find My app BEFORE the iPhone was lost. Here is some information on that app ➔ If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support.

Note that your lost iPhone must be able to make the connection to the internet via Wi-Fi or cellular connection so that it can mark its location and broadcast it. 

Axel F.

There is nothing that I can do about this. I am a user of this forum just like you are. I do not work for Apple. Apple will not be able to do anything either. If the iPhone is offline then you will not be able to locate it.

Axel F.