How can I locate lost or stolen Iphone

See the following from If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

Find My [device] is the only way that you can track or locate a lost or missing device. If Find My [device] isn't enabled on your device before it goes missing, there's no other Apple service that can find, track, or flag your device for you.

By physically searching for it, posting notices around where you lost it, and if applicable, contacting the Lost and Found department of the facility where you lost it.

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