It could have been a reported as a false review or self-review. For example if the reviewer is using the same computer as a provider, thats one way that TER admin can determine it. Also sometimes TER doesn't catch review problems with their initial approval and the problem may have been reported later. Providers may also request delisting but that will remove everything and prevent future ones as well.

The reviewer may have asked to edit the review for any number of reasons, in which case the review will vanish until the edited review is submitted and approved. The one time I did that the second approval took much longer than the initial approval.