lost phone

If you lost your iPhone, and if it says it’s offline and can’t be located, then it will not ring. However, while you are searching for it, put it in lost mode so nobody will have access to your data. If somebody else finds it, they will know who to call and they can’t get into your iPhone.

No, if it is offline.

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

Regards

Giulio

Maybe, or the battery is dead.

That's a 3rd possibility, yes.

My pleasure :)

Best of luck.

Giulio