I would check the ‘Document Properties’ of this calendar event… to see who/what last modified it.
To do this, go to the “Day” view of the calendar (March 7) and locate the appointment. Right click on it, and choose Document Properties. When the Info box comes up, first look on the 1st tab to see date last Modified, and make a note of it. Notice if it is different than the Created date?
Then click on the 2nd tab of the Info box, it shows fieldnames on the left side and info about those fields on the right side. Locate the field named “$UpdatedBy” on the left. Click once on it to highlight it… and then look across to the right side and see who the person was that last updated it. Perhaps someone DID reschedule it and just hasn’t admitted to it yet?
This will tell you for sure.