Perhaps you have seen the Ogham (or Oggam) alphabet? Supposedly it was designed for messages written on a notched stick. Like this from Ancient Origins:So, as far as I can tell, this writing system is common in the Southwest, because I keep seeing examples of it in videos. Like this one from "Trek Planner", who goes out in the desert near the 4-corners area and makes Go-Pro videos as he hikes and
