Non physical is a label for alleged phenomena beyond our science.
The only thing that is "beyond our science" is pretending that there are things beyond our science, and that happens because of simple human ignorance. I don't think that is what Learner meant anyway, so still waiting.
I Havre no doubt there are aspect of reality we may never be able to see or understand. The idea that science can know all and see all is akin to theism.
The first inkling of the infrared spectrum came when someone noticed a hand go warm near a prism without visible light.
Serendipity has always been part of advancement. Look for one thing find another.
The CMBR was discovered when people testing an antenna could not resolve where noise was coming from. U Of Illinois I believe.