A scientist or rational person develops a theory (not a hypothetical scenario, but a theory in the scientific meaning of the word – a group of propositions based on evidence that can be tested, form predictions, and withstand experiments intended to dispute the theory’s validity) about the nature of reality and is willing to change his/her worldview based on the results – no matter what the results point to. Scientific theories are falsifiable, no matter how much we grow accustomed to understanding reality as we know it. If, for example, the age of the universe were somehow proven to not be 13.72 billion years old and, say, 5 billion years old, then scientists and reasonable people (with valid and tested evidence) would have to accept that their understanding of reality was not accurate in the past. They would feel compelled to remain intellectually honest and accept the new paradigm, even if this new evidence challenged some sort of philosophical ideology they had formed based on their understanding of the universe. This would also prompt them to look at other theories to see if similar problems could be detected and rectified.
The problem with religion is that it is not falsifiable. It is simply a laundry-list of assertions based on zero evidence that cannot be tested, used to form predictions, or falsified by any standard of rationality. Religious claims are made deductively – starting with a predetermined answer (God created the world, there is a Heaven and Hell ,etc.) and moving backward to support these claims with “evidence.” The problem with this is that is traps the human mind in a web of assertions that cannot be disputed, and are not permitted to be questioned. This, regardless of how a person might experience life under the control of religious parents, a religious society, personal religious guilt, paralyzing fear of the unseen, etc. Read “Infidel” by Ayaan Hirsi Ali for a sampling of the dangers of irrational religious thought based on non-falsifiable beliefs.
Side note: Let’s say everyone on Earth has sudden amnesia. Could their experience on Earth lead them inevitably to believe – and test – that gravity exists? Yes. How about characteristics of human behavior and well-being? Yes. How about the existence of the archangel Gabriel? Not likely. An amnesiac would need to form a worldview based on what is there, and he would certainly not inductively reason to the point where he would have re-created Christianity or some other religion based on any rational understanding of the world.