Yeah, I can confirm I've seen it in Melbourne.
Not in Springvale though - more so in Noble Park... that back bar and side skirts... I swear I've seen it.
If I were you, I would contact the Victorian Police and give them your VIN number... they'll put it on their register... so if they randomly pull people over with a similiar description, they can do a check... don't worry, in Springvale/Noble Park area - cops pull Skylines over all the time, You should be able to find it quick... good luck...
It was driving pass Springvale road towards the lights leading to Noble Park station... the driver was an Asian guy in his late 20's - looked like a street-wise kinda dude... I remember, as he pulled up to me and wanted to drag me - the Mrs. and I joked about how he would have no chance so I remember quite clearly... hope your brother gets his car back mate... ring the cops asap!!