Foreign Student.
I believe the aircraft mentioned (flown by a young female student from the sub-continent), left YSDU mid-afternoon headed for YSBK. Upon departing YSDU, I overheard Centre calling an aircraft west of Mudgee tracking south east at 7500'. There was no reply. As Richmond restricted airspace was active at the time, Centre was no doubt trying to worn the pilot, to no avail.
I was assuming that the aircraft mentioned by centre was indeed the one mentioned here today, as it was the only aircraft in the area. The registration mentioned above confirms that. So I suppose thats the answer to your question!