How does one obtain proof that a non-refundable ticket is fully forfeited and has Zero value?

I had a ticket booked with Chase Reward Points from my wife's Chase Sapphire Reserve account and had purchased a Travel Insurance Policy that includes trip cancellation coverage. I am aware that Chase has trip cancellation coverage too. It is secondary coverage. I have filed claims with both companies.

My wife broke her arm 4 weeks before the trip which was scheduled in 2 weeks from now. We have cancelled the trip. Best case is she is in a cast in two weeks from now and she doesn't want to travel that way. This trip includes two overnight flights in a row in J but I agree with her that it would not be fun with a cast even in J.

I called Chase Travel to cancel the flights which they did for me and sent me an e-mail indicating there was no value on the remainder of the tickets as I had asked. This turns out to be wrong as Korean airlines still shows the ticket as Unused and Open. I confirmed by calling Korean that the reservations were cancelled but that the ticket is still not cancelled. According to Korean even if it was cancelled they will not provide evidence of no value remaining and I have to call Chase to fully cancel. So I will call Chase back.

My question is how to prove to the insurance company that a ticket is cancelled, unused and the value if fully forfeited. Any help would be much appreciated.

Thanks.