If it was never recalled 20 years ago, it has always been a current chip.
Maybe a little hard to get but still a live chip.
You could have forced them to cash some, in the last 20 years if you had wanted to.

A friend just ran into the same thing at the LV club. They would not cash chips because they no longer used them, but they had not been recalled. He ask where the phone was so he could call gaming and they desided to cash them.