I happened to be in New Orleans after the boats closed their casinos and there was a land-based office redeeming their chips. I tried, but was unable to buy any of the chips they redeemed so I imagine any uncancelled chips you find were chips taken home by tourists who missed the redemption period. It's always possible a hundred might have been kept, but I'd doubt the $500... you can fly to New Orleans and redeem it for less than $500 [g].