Let's assume I witnessed such an extraordinary event. A person who was clinically and legally dead for 3 days--no cardiac activity, no respirations, absent brain stem reflexes, a totally flat EEG with all channels set to the highest gain, and a body temperature equilibrated to ambient conditions--had returned to life without any technological intervention. People are saying it's an act of God. I would have no alternative explanation. But l'd ask how anyone could be sure that this miraculous event was the act of their particular god apart from the thousands of gods that humans have worshipped? Could it have been the work of an unknown extraplanetary entity using advanced technology undetectable to us? Or maybe an evil, demonic agent, masquerading as a god just to be deceptive?
In the end, all god-beliefs come down to faith. Christianity is no different. Christians have to have faith that whatever leads them to believe is real, that the Bible is true and accurate, and that God and Jesus are as the Bible and their religious tradition says they are.