Actually, there was a woman this happened to. It's a very sad and scary condition.
http://abcnews.go.com/Health/memphis-woman-world-fingernails-growing-hair/story?id=16974423
why nails grows in the fingers and not in the face?
As you have asked the question can I also ask such question? Why do you have teeth in your mouth only, why shouldn't on the head?
It would be creepy If nails grew in our face therefore they grow on our fingers instead.