Ripple's former CTO acknowledges loss of private key loss 7002 BTC

Ripple's former CTO Stefan Thomas said in the AMA that although he hopes to promote mainstream adoption of BTC, the inherent limitations of the BTC blockchain make him bored. He also admitted that he had lost 7002 bitcoins. This was his bounty for the bitcoin video. However, his private key was lost. He said that it is almost impossible to retrieve the private key.