When a booking or a rescheduled booking is made and it requires the approval of an attendee, it will appear in the Pending tab of the Bookings section.

However, pending books expire in 72 hours.

When they do, they will not be shown as Past sessions until the date is in the past or as an Upcoming session because it was not accepted. Therefore, they seem to disappear.

This is a known issue that we're looking to address in the future.