Life interrupted

You're sitting down, finally able to concentrate on something you need to do; let's say, something your need to read, or write, and someone else comes to tell you a never ending story. Your mind wanders toward what you were doing. Your colloquist demands your undivided attention. Your mind wins right at the moment when you're supposed to interject in the other person's conversation...Don't you think? is the question and you have no clue what the conversation (or monologue was about)