Why Won't God Heal Amputees?

God won't heal amputees because it is impossible. "If you believe, you will receive whatever you ask for in prayer." noone in their right mind would pray and actually believe that their arm would grow back. there is no way to truly believe that it will grow back. But in my opinion, amputees are healed every day. its called a prosthetic limb. I don't know if I would say that God did the healing but in some sort of way, they are healed.