Find friends apple app to locate an iPhone

My brother's iphone stolen and its find my iphone is turned off. but he has "find friends" apple application installed and working. i logged to his find friends app account using my iphone and accepted my invitation to be friends and then logged out and now he is in my friends list but it tells me location isn't availabe.. yes because the mobile is switched off.. so my question is when the mobile is turned on can i locate the phone. the iphone on mobile internet package and dont needs wifi.. and when i logged into his account thats mean the another account signed out or its still signing in? and should find friends app running to locate or it may be not running.. thank you.