Deja Who?
I dunno, it was right on the tip of my tongue.
When you DO remember; but a bit too late it’s called esprit de l’escalier; For when you have the bon mot [the witty reply] but only after you’re halfway up [or down] the staircase.
I personally have a terrible disease it’s called Sometimers; sometimes I remember, sometimes I don’t.
While aphasia is technically due to brain damage, I have oft heard people describe the experience of not being able to come up with the word they want as being aphasic.