Best to keep an open mind, when we don't know.
We know that the human brain is an imperfect memory storage device. Mess around with the chemistry of a brain -- through disease, trauma, or otherwise -- and memories can be changed or erased. This has been proven. Why should one consider it likely that observable physical evidence in the world had changed by interaction with another universe, but the brain's electro-chemical pathways remain unchanged?
"Mainstream" science is a very fleeting thing. As such, it shouldn't attempt to set itself apart as something superior and basically tell the layperson 'Sit down, we've got this'....as if the average person does not have the capacity to even begin to intelligently evaluate happenings in his or her own life, but that science will save the day and pull them out of their uninformed and valueless musings.
When mainstream science insists upon conducting matters in the same manner as in centuries past, without keeping an open mind, it amounts to this:
You are not talking about science, but some kind of caricature of it. Science is a process of questioning, observing, testing, predicting and skeptically evaluating evidence, which is by its very essence open to revision. In your post you point out that quantum science is looking into multiple universe theories. But, if something in that field is proven, with evidence and verifiable predictions and observations, that would become the very "mainstream science" which you have called out as arrogant above.