Find my Friends needs both parties to have an Internet connection
Nowhere does it say Find my Friends needs both parties to have a live Internet connection (WiFi or cellular) at the time they want to find a friend. That may be obvious to most, but I've just helped someone who didn't realize that. You must have an active connection to iCloud to ask for another's location, and they need the same to get the request (and send back their location) ..
iCloud-OTHER