The onus is on you as the seller to remove the vehicle from your name. Bad mistake, also been there, done that. Write off the licencing as school fees.
I sell quite a bit of vehicles (as a 2nd income / hobby), and I make use of a company called "WeQ4U" for all my admin related inquiries for licencing. They are pro's when it comes to these issues, and they do not charge an arm and a leg.
If you still have a copy of the sellers ID, and a proof of residence, you can simply remove the car from your name, WeQ4U will charge R190 for this service, and you can email all supporting documents. (I did one of these yesterday). Note that licencing fees need to be up to date to do this.
Scrapping a vehicle is a different story, you need to obtain the original registration certificate. If you have given this to the new buyer, or if you have lost it it is possible to obtain a copy. If the car was financed, and registered on your name after you paid the car off, you can obtain a copy from the licencing dep.
If you never bothered to put it on your name once the bond was paid off (most people do this), you can request a duplicate certificate from the finance house (they normally charge a fee for this).
To avoid any further "I think do this" and "maybe do that", just get in touch with a lady called Elizabeth from
http://www.weq4u.co.za/, she is a champ.
Edit: They also go to the licencing dep, and submit the forms on your behalf, so you dont need to go back and forth the whole time