It's not just "not obvious" - it's not used at all. ...and hasn't been since 1945. ...and even then it wasn't known except to the people in a few camps.
...so what's your hypothesis here? That he told them to use a near-nonexistent symbol as a secret message to the, maybe 5 people in the world that remembered that symbol?
Does that sound like a credible theory to you?
...or isn't it more likely that some stupid intern just fucked up?