As people have written a thousand times so far, the finger print isn't saved off device. Yes, it is saved. But if someone can get your device, they can also get your fingerprint (probably from the screen of the same device).
But again, I'm much more concerned about all the other information my cell phone operator, so this is quite simply just hysteria, and undermines the rightful concern us techies have about surveillance.
If you are worried about being specifically targeted, you shouldn't use an off the shelf cellphone at all, and this discussion is moot.