About how can we find a iPhone stolen or lost I said in other articles on iHowTo.Tips.
So far, Apple has a very good location system of iPhone. The condition is that iPhone not to be turned off (Power Off) or not to be completely reset. Assuming who found him or stole it he knew code PIN or unlock password iPhone and somehow managed to get it reset completely si to delete all his data from him.
Starting with iOS 15, iPhone will behave like a AirTag. That means the device it can be located even if it is completely closed or has been reset to the factory settings.
The U1 chip present on all models of iPhone 11 and iPhone 12 is responsible for locating the devices, having a low energy consumption. U1 will remain permanently active on iPhone and will send the owner exact location data. It will become quite risky to buy a iPhone stealing.
Many owners iPhone I do not know these devices are registered in the network Apple based on an account. Apple ID or account iCloud.
When the activate a iPhone, iPad or alt device Apple for the first time, it will be automatically added to your list of devices in your account iCloud. Completely resetting a device and deleting all data on it will not remove it from your account. Those who sent devices Apple In an authorized service, I know that before shipping or delivery you must enter the account iCloud and remove the device from "My Devices“. Precisely because if the product is replaced, the old one can be reconditioned and used by another person.
Another feature that will present you on Find My with the launch of iOS 15, it will give users the opportunity to be alerted when they forget a device somewhere and leave. All we have to do is go to the list of devices in Find My and to activate "Notify When Left Behind" for AirPods, AirTag, iPad or any other device.
About how the network works "Find My" to Apple, you can find more explanations and details in the article: “iPhone stolen or lost? Find out how you can recover it very easily“. The article will require a update as soon as iOS 15 will be available to the general public in the fall of 2021.Location iPhone even if it is closed or deleted and reset to factory settings [iOS 15 Find My Network]