I have seen a few unfilled in triangles which mean that there is an unfound location. One was near 3 Maries cave. I literally went into TCL and cannot for the life of me find what I think I am supposed to. It was near Mary’s cave that I found that I was able to enter Mary’s cave and exit it without ever triggering the fast travel spot. I later walked by it and BAM I got it. Weird. I have one survivalist cache left to find and am annoyed at not finding it.