I found out later that you could have exchanged them at the Yes GFTO 1977 Show.
I had tickets for this show. As I recall the promoter took the money and left town or something like that. The City passed a new bond ordinance, as a result making promoters put up a bond equal to the ticket sales.
We bought our tickets in advance, through the mail, I believe (24 years). It would have been my first Yes show. The concert was canceled, with no explanation. Refunds were offered, but the ticket broker, Satellite Tickets, went out of business before I could return my ticket. The story was that Satellite used the Yes ticket money to cover another debt, then were unable to pay Yes.