how to find iPhone when not logged into iCloud?

Nope. Your only option is to look for it the old fashioned way and trace your steps. Please note that if Find my iPhone was not enabled, if someone found your phone, they can easily wipe it, set it as their phone and you'll never find it.

Contact your cellular provider to see if they can blacklist the phone, which will prevent them from activating it. Also, change your passwords for everything you can ever access on that phone. Passwords for Apple ID, bank accounts, email accounts, apps, etc.

Hi ipittacus

Sorry to be the bearer of bad news but there is no way to find this device without find my iPhone enabled you cannot lock it down either without find my iCloud enabled. I would advise contacting apple and tell them the serial number of the device they may be able to help you further

Your advice to contact Apple will not help. Apple will NOT get involved in lost or stolen devices in any way at all. Since the OP did not use the easily available Find my iPhone or connect it to iCloud, there is no hope for him to track the phone at all.