If a contract was established, and you were prepared to honour your side of the agreement and pay R10 000, the claim would be for the delivery of the bike in question or for damages. The choice is yours.
You may think that this is all theoretical but happens everyday when contracts of sale are breached and the aggrieved party chooses to exercise their rights under the contract.
There are no specific rules for the sale of secondhand cycling equipment, and most people just allow the guy to get away with it, rate him down and then complain on the Hub, which actually is the rational approach.
Your reply is in response to my comment that said I would issue summons in the small claims court. You may choose to do something else. I would choose to make the guy see the error of his ways, and make good his breach.
You say above: "R10000 - the price of the Bike ( which you haven't paid anything for, but you believe you you have some rights too)"
It is not a belief, it is a certainty.
If a contract has been established and the sale is perfecta, not only does the buyer have rights, but so does the seller even if no cash or bicycle has been exchanged. You are entitled to the bike and he is entitled to the R10000.
IIRC, one of the consequences is that risk passes upon the contract establishment and if (through no fault of his own) the bike gets damaged or stolen before he hands it to you, you must still give him the R10000, and hope your insurance company will pay you out for your loss.
It may not appear fair, but chat to your lawyer and check it out.