Was just playing back some of today's aircraft activity on Webtrak on Airservices' site. Interestingly there's an unidentified aircraft coming down Victor1 showing an altitude of 403.5 feet. It appears to emanate at Maroubra at time 2:18:56 heading south then it and all the other aircraft suddenly disappear at 2:20:00 (like the feed into the recording system dropped off momentarily) and then start re-appearing gradually at 2:20:53. This same unidentified aircraft never reappears. Could this be the mystery machine in question on it's way to Cronulla and to a lower level than the 403.5 feet being initially reported?