Let's say that it's scientifically proven that ghosts exist. Would they then stop being supernatural and become natural, thus making it impossible to ever have proof of the supernatural?
Last I was aware, the idea of human culture being "superorganic" referred to the idea of our culture itself acting as an organism above the individuals that compose it, i.e. a superorganism.
The concept being based on emergent behaviour observed in colony forming insects (I.e. ants, bees, etc.) to act as an apparent single larger organism.
That isn't the same as the concept of the supernatural, where it refers to things beyond our understanding of nature.
Not knowing the exact cause of a natural phenomena doesn't mean that we don't understand how it fits into nature - if it exists, then it can be understood, ergo not supernatural.
It's not that I don't like it, it's that you give such a vague definition as to what qualifies as supernatural that damn near anything you feel like could qualify.