I so hate that feeling of not being able to retrieve a word. it is not like I forget it, it is more like the word has been completely erased from my stored vocabulary. I can visualize exactly where it should be coming from and there is a huge blank space. If I look up the word , I can sometimes make it stick again.

YaYa, I so sympathize. I used to have a huge vocabulary, tonight at dinner I could not remember the word agile to save my soul. My B12 tested fine, but I am considering supplementing anyway.