jeeezuz h christ!!!
its only a car mate, you sold it to him end of story!!!!!
who really cares what he did with it from the moment HE bought it off you.
that means you no longer have ownership of the car. ie.... its not yours!!
your just making yourself to look like a sooky la la.

i sold a 2 seater 260z to a cousin for 2500 only for him to onsell a few weeks later for 5000. maybe you should have sold the 2 door for more money????

ps...
what does an abn number have to do with selling a car, unless your making threats to tappet about other matters.