This seems to be the crux of the issue:

After CBC Toronto contacted TD this week, it offered to issue a new cheque with the condition George sign an indemnity agreement, which means he would be held liable for the money if the original cheque is ever found and cashed by someone else.

George says he declined, and instead offered to sign an agreement that says he'd be liable for $150,000. He says he isn't comfortable with the risk of having to repay the full amount. He also says he's done nothing wrong so shouldn't be the one on the hook.

So it seems that this offer has been made, but on the condition that if the original cheque is ever found and cashed Kavaratzis would be on the hook for it. Kavaratzis contends that that's not fair as he wasn't the one who lost the original.