Good point

I've never played chess in my life so other than the "light and dark" aspects used, I know nothing haha. I know backgammon was played by Walt and Locke on the beach. So lets see if I can make a list of all these instances:
Locke and Walt play backgammon (not sure if this is like chess or not lol)
Locke plays chess in the flame station
Locke and Ben both play chess together
Jack and Ben also play chess together which is shown in one of the new missing pieces clips
A chess set is shown on the table when the strange visitor comes to see Hurley in the Asylum
I bet if we went back through episodes we'd find out that there are more chess playing instances or maybe random chess games in the background lol