Destruction of the subject matter of the contract?

You agree to sell your kidney for $10,000
Crazy Cannibal Carl accepts your contract and signs it.
Doctor Dumb removes the kidney and promptly decides to eat it.
( Destruction of Subject Matter - Since The doctor destroyed the subject matter of your contract Crazy cannibal carl is no longer obligated to pay )
Crazy Cannibal Carl upon hearing this rips up his contract and eats you instead.