Identity of a supposed anonymous referee revealed through "Description" of the report I received a referee report from a journal (with single blind peer review policy). 

If that matters, the journal uses "Editorial Manager" system.

By clicking on "View Attachments", one can see 5 these information "Action", "Uploaded By", "Description", "File Name", "File Size".

The content of the column "Uploaded By" is "Editor".

The content of the column "Description" is  "from prof. X"

Hence the identity of the referee is disclosed. 

I am wondering if it is an unintended mistake from the Editor or it is the referee who has written such description. 

The referee has done a substantial work to evaluate the manuscript and has proposed many suggestions leading to the improvement of the manuscript.

My dilemma is that, as I know the identity of the referee, should I use his real name in the acknowledgement or just thank an anonymous referee?
If the review itself is not signed, it sounds like the unblinding was not deliberate. I would:


Reply as if the review were anonymous 
Notify the editor in a separate, private message saying there may have been an error in showing the reviewer name