The file can not disappear by itself. So, one of my points is correct since you have seen with your own eyes that the backup archive does not exist. Please review all your settings especially since you are the only administrator. It could be something as simple as setting up a quota setting without remembering it or something as complicated as having set up a script which ends up removing the old backups outside of Akeeba Backup.
It is fairly obvious that there is nothing I can help you with any further. The interface is correct in saying that the file does not exist, so no problem there. The reason the file doesn't exist anymore is ultimately one which comes down to user-initiated configuration or a user action. Therefore I will now close this ticket.
Nicholas K. Dionysopoulos
Lead Developer and Director
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