Exchange 2010 Orphaned GUID

The following error kept being thrown in our Exchange 2010 Application event log:

Event ID 9554
Source MSExchangeIS

"Unable to update Mailbox SD in the DS. Mailbox Guid: 0XXXXXXXXXXd. Error Code 0x8004010f"

(GUID obscured)

The Microsoft articles for this are as follows:

These state taking the mailbox GUID and converting it back to the AD GUID and then fixing permisions.

When I tried this in our enviornment no results were returned.

Digging deeper I tried searching our maiboxes for the GUID:

get-mailbox | ft ExchangeGuid, DisplayName

The GUID was not evident in this list.

The only other place I could think of a GUID hiding was in the disconnected mailboxes so ran the following on each database to see if the GUID came up:

get-Mailboxstatistics -Database "DATABASENAME" | Where-Object {$_.DisconnectDate -Notlike $NULL} |FT DisplayName, MailboxGuid

The GUID was found - wahoo.

Next I ran:

Remove-Mailbox -Database "ICT" -StoreMailboxIdentity 0XXXXXXXXXXd

And waited, checking the event log later in the day and the event ID was no longer showing.