As explained to me just today, InDesign finds characters based on Unicode and whether the .alt glyph(s) appear in an OTF feature within the font.
My issue is that my .alt glyphs are showing up in the InDesign glyphs palette with the name "NULL", which I don't like since they do actually have names. I'm looking for a workaround to that today.

Charles, you wrote: "Actually, all I really know is that as soon as I associated the glyph with another glyph that had a Unicode number via a OT feature, the problem went away."
Can you give an example of how to accomplish this?