iCal appointment history disappeared

Recently, on my iPad, I went to the Settings -> iCloud and enabled my Calendar. I do not regularly plug my iPad in to iTunes for backup and wanted to back up to the Cloud.

I then received the notification to update to the most recent IOS, which I did (read: I did complete the update).

Since the above was completed, all appointments (that were entered before the two steps above were taken) that were in my Apple Calendar app have disappeared. I do not know how to go about retreiving them.

Please help.