iPhone offline and location not found in iCloud

"Offline" appears when one or more of the following conditions are true:

• The battery has run down
• The phone has been powered off
• The phone does not have an Internet connection
• If the phone was stolen, the thief has wrapped aluminum foil around the phone or put it in a Faraday Bag to prevent the phone from either sending or receiving a signal

Unfortunately, there is not really anything you can do about this except check a few times each day to see if the status of the phone has changed.

The only way you can locate your iPhone is in Find My. If it shows "Offline" or "No Location" found, it’s likely your iPhone has run out of battery or has no connection.

Also please review the following article:

Find your lost iPhone or iPad - Apple Support