Finding a lost phone when find my phone is off

Sorry, see the following from If Find My iPhone or Find My iPad isn't enabled on your missing device - Apple Support

If your missing device doesn't appear in the Find My app or at iCloud.com/find, you didn't turn on Find My. There's no other Apple service that can find, track, or flag your device for you. But there are steps that you can take to help protect your data.

See the rest of that support article for the other steps that you can take.