A few minutes before the meeting, you slip away to the washroom. When you're sure everyone has left, you go back to your desk and resume work in the peace and quiet of an empty office. A few minutes before the meeting is scheduled to end, you slip away again, and only return when everyone else has. No one will know if you were there or not with 50+ people present. If someone shows up during the meeting you say you forgot, or you are working on this critical task or whatever.

Been doing it for years.