That’s fascinating. I have something a teeny bit like that. Every now and then, a word doesn’t come. I speak the sentence without thinking about it – as one does – and I might get half way and the next word, a noun usually, is suddenly not available. I know that I know the word. It’s never something arcane or unusual, like turnbuckle or arcane, just a regular word, but I stop because it has retreated away from whatever mechanism I use to pick the next word in my life.
I get it back within a few seconds, but it feels like I’m losing my mind and I wonder what will vanish next.