As others have mentioned, having the message from the Buyer should be all you require to have it fixed, but I have been hounding CS since October with a similar situation (Buyer accidentally left low DSR's for Item as Described).  While I have 3 messages from eBay confirming it was an error, they can see that in the messages and so the Defect will be removed - I am still waiting - and messaging !

So I do hope you have more success than I have had - it's a pathetic system !