I run the conversation over my head to make a corny and witty and maybe punny come back... if it is not convo, idk
i pretend to reply to a text and act like nothing happened and i'd say what were we doing/talking about majority of the time the other person would change the subject or say they cant remember either... works for me all the time...
Weasel out of it somehow, excuses, denial, whatever it takes including getting up and just leaving the place for a bit (sometimes the best) or I'll just redirect the conversation too something else.