How to delete messages from a user already deleted

[MediaFolSupport]

Hello,

we have deleted a user account on his request.
now he see messages in the forum with his name, (as a guest, of course), and he asked to us to delete all his messages...

From admin control panel i cannot find any more nor his account nor his contents... how can i find/delete content from a deleted account?
thanks.
How to delete messages from a user already deleted

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