Locating a lost iPhone without Find My or iCloud

Without Find My, there is no way for you to electronically trace the location of the phone.

Carriers will generally only trace the location of a phone by IMEI in exceptional cases: e.g., a missing persons case where they have been presented with a court order. They wlll not do this for a phone that is merely lost or stolen.

If you have reason to believe that this phone was lost within a confined area, like your home, you could try calling it from another phone and listening for the sound of "ringing". Maybe you'll get lucky. But if that doesn't work, you'll have to look the old-fashioned way: without electronic help, by hand.

As for disabling the phone, hopefully it was locked with a passcode that others do not know and cannot easily guess ie.g., NOT "123456"). An iPhone will only allow people to make so many incorrect passcode guesses before it goes into a state where the only way back in is to reset it and wipe all of the data on it.

Because Find My was not enabled on the phone, you will not be able to mark it as Lost or request a remote Erase … and anyone who finds the phone will be able to hook it to a computer, reset it, and "make your phone their own".

You can contact your carrier (or have your workplace contact your carrier, if it's their phone), and request that the carrier blacklist the phone. That would prevent the phone from ever getting cellular service from any carrier who honors the blacklist.