Here's my experience finding one small gold bangle left in a security tray 'somewhere'!
Went through ADL on the way home the other day, settled into the lounge then wandered back to security where I found a supervisor strolling the security area. Asked if there was any record of items left behind in security trays and explained my predicament. Invited me over to his 'desk' where a folder had a sheet for each day listing items left behind. Unfortunately my gold bangle was not listed so at least that told me that it was definitely Sydney I was now needing to contact.
So in a most impressive to and fro of email communications from the Lost and Found at Sydney International Airport, and after me having sent a photo of my bangle, they were able to say yes, item found and provided a reference number. Collection could be either pick by myself, someone else with an authorisation letter or courier to which I was given details.
As said I was most impressed with service at either airport for security and their documentation of what items are retrieved.
Personally am extremely grateful to have my 50th birthday gold bangle found and will be more careful as to how I put it through security checks in future.