I have had that happen too, once when I then saw the items being sold by another seller (and I could show it was the same item) and so similar to your deal where someone had made a higher offer after the deal.

I have also had at least 2 bids cancelled before the end of the auction on sales where I then see the items (both were for more than one chip in a sale) being sold by others. In both cases my final bid was way higher than my opening bid as shown and I usually let the seller know that I hope they received a good price for the item as this is what I would have paid.

Unfortunately you have to let it go and just avoid dealing with them again (although in my cases I don't think the originally sellers were usually sellers of casino items)

Jason