Readers should understand that the term unicorn has a particular meaning--somebody who seems to have discovered all on his own that OC is legal, no open carry website, no news media stories about OC, and just up and decided to start OCing. It does not denote an OCer merely unknown to the observer. The term unicorn arose in the early days of OCDO because it was judged the somebody who did that--all on his own realization that OC was legal and just started OCing--was as unlikely as a unicorn.
Otherwise every OCer not known to the observer becomes a unicorn. We already have a term for someone who is open carrying: open carrier.
If the criteria for being a unicorn is merely being unknown to the observe then even I could be a unicorn. But, I'm not. I learned about OCDO and OC from others in the self-defense rights movement.