The problem is that it's a bank draft, not a cheque. The whole idea of a bank draft is that it's guaranteed by the bank, so it can't be unilaterally cancelled after it's been issued. It's why you only accept a bank draft when selling a used car; once you have the bank draft, the other party cannot cancel it. The funds have already been removed from their account and are being held in trust by the bank.

It's a sticky situation. TD doesn't want to be on the hook for $300K should the original draft be deposited, but they can't cancel their obligation to that bank draft unless it is surrendered to them.

Meanwhile, Canada Post doesn't insure mail to the tune of $300K. They would have needed to buy separate insurance ahead of mailing the draft.

I don't see how this can be resolved at this point, even with media attention. $300K of cash should not be sent in the mail without adequate insurance.

Essentially, how would this story be different if they were literally shipping a box of cash by registered mail? I think it's pretty clear that that's a very risky thing to do.