Now as I review this thread (and find one of my very own typos),I understand "missing glyph".
I wonder if Jim Allan and I are "on the same page" when we
speak of "missing glyph"? It means something very specific
in the font jargon.
But these days different applications behave differently when there is a missing glyph, sometimes doing something other than showing the missing glyph symbol within the font.
Jim Allan