Participant shows in recording despite pinning host

I recently recorded a meeting and one of the participants periodically appeared in the meeting despite my not seeing this while the meeting was taking place and being recorded.  I believe I pinned the screen that we wanted to record.  All participants were muted.  I did forget to end recording prior to ending the meeting, though I was able to retrieve the meeting from the cloud later, and I don't see how this  would relate to that problem.  I  just would like to know what I did wrong so that it doesn't happen again.