I went to NSW State Archives at Kingswood yesterday :
On Reel 2765 is the register of Coroners Inquests 1914-1920 , and reference 1920/24 is the Unknown man found at Prospect. Held Jan 8 through Jan 10 , nothing you did not already know , the verdict was "Heat Stroke following on lying out in the Sun" The story is also in the "Cumberland Argus" 10/1/1920 on Trove.The Staff at the Archives indicated there was no further information on the inquests.
The Police Gazette for 1920 are on Reel 3600 at the State Archives , I was running out of time , and as there were 4 Gazettes in February. I could not find the report - Have you seen it ? - I was looking for Parramatta and have just reread the fact it was under Balmain