It was there about a year ago - I remember finding the mobile number of an ATO to contact for some flying.
I tried to find the website again late last year and found nothing. It says the webpage has been "archived". If you search "authorised testing officer casa" on google it should be the first result (I cant link it as I have less than 10 posts).
Also I take it from the CASA website that the term ATO is being phased out, and instructors with Flight Examiner Ratings are now the term to be used (not sure what the difference is... I gotta do some reading).