To find a lost iPhone, open the Find My app on another Apple device or sign in at iCloud.com.
It helps to understand what's happening under the hood, because it changes how you react.
This is the feature everything else depends on.
From a computer or someone else's device, sign in at iCloud.com and open Find My (or use the Find My app on an iPhone or iPad).
If the phone is offline or dead, Find My still shows where it was last seen.
Read the complete breakdown, fixes and what happens next.