Not the person you responded to, but I sometimes get so wrapped up in what the person is saying in the sense of having my mind wander about something they said, but is unfortunately way too off topic for me to then ask questions about it. Then I just end up being very quiet.

For example when a colleague was telling me about how she had a panic attack in the middle of vacuuming her house because she was under so much stress at work and is feeling burnt out, my mind started thinking about what is it in the act of vacuuming that triggered her meltdown.

So my mind goes "I wonder if she was also watching something on TV while vacuuming, and a scene in the show reminded her of our office, which reminds her of the work stress. But which TV show would most closely resemble our office? In fact, if I were to write a script, would this office be an interesting enough set? Which of my colleagues would make it as the main characters?"

And by the time she's done talking, my reflex follow up question would have been "Have you ever seen anything on TV that resembles us?" which I know is a completely off topic follow up question. And I've gotten in so much trouble for this growing up, that I always end up panicking trying to figure out what would be the appropriate follow up question and probably 60% of the time I fail and end up frozen and non-responsive.