Merci!

You are having a heated discussion with someone. You feel that little "ouch" in your soul. You leave and on the way home you think of a million things you could have said to that person but it is too late.
The expression for this occurence is French and has the word "stairs" in it which when translated from the French would mean sorta like "a witty repartee from the stairs".
Anybody?

l'esirit de l'escalier
The spirit of the staircase. Earlier discussion available (type staircase into search box)

I searched via all sorts of keywords except the obvious.
thanx
bk