How to locate a lost iPhone without Find My iPhone?

Sorry, but it is not possible to locate the iPhone online if Find My was not enabled on the phone.

All that you can do is physically look for the phone in the area where it was lost and ask at restaurants and shops that you visited to see if someone turned the phone in to the manager.

Read this support article to learn what you can do if Find My iPhone or Find My iPad isn't enabled on your missing device --> How to find your lost iPhone or iPad - Apple Support

If you simply misplaced the iPhone, have you tried calling it and seeing if somebody answers? If you do this, be careful because you do not know if the person at the other end is somebody you can trust. Have them take it to a police station or a lost-and-found service where you can safely retrieve it. Do not provide them with any account information. It could be a thief who found it.

I agree with Bob Timmons

You may read this to understand the other ways to protect your data. --> Do's and Don'ts for lost iPhones - Switch… - Apple Community