Whilst flying back towards 2RN from a flight in BK training area had SYD CEN warn a Citation of a unidentified Aircraft 5m North/West of 2RN at 1,100ft, which no other aircraft (3 total) could visually locate including myself nor was their a response from a aircraft that would have fit that location and height by the time i switched frequencies to bk (good 5-7 min from first announcement) their was no sighting nor response to it.
I Know its kinda off topic to Cronulla sighting but strange