Friend of mine lost his iPhone how does he find it...
e-mail NSA
With the find-my-phone app via another device logged into the same icloud account. I have misplaced my iPhone in the home or car, and can track it via my Watch, Mac or iPad. I can also make the iPhone ring when I'm close to it in order to find it. The secondary device will show a map of where the lost device is pinging from.
If he turned on "FindMyiPhone" he merely needs to log onto his AppleID account from any computer with his AppleID and password and go to the FindMyiPhone tab. . . it will show the current location within three feet.
If he has an AppleWatch, there is a button on the Watch that will cause the iPhone to play an audible chime every time it is pushed. If the iPhone is in the house, he will hear it. Swipe up on the AppleWatch screen to expose the control screen; the ping connected iPhone button is there.
Apples website for that is actually quite excellent.