I came across this excellent old Desert Inn chip just listed on eBay this evening... I put
in a bid, became the leading and only bidder, but about two hours later received a "bid cancellation" notice from eBay stating that the item was "no longer available."

It was my understanding that an item could be withdrawn from eBay by the seller if...
1) there were no bids, or 2) there were factual errors in the item description... but now I see that an item can be withdrawn at any time and for any reason - in this case I suspect that another collector contacted the buyer outside of eBay channels and made him/her an offer.

My question is this - does this kind of thing happen all the time on eBay, or was this an unusual occurrence?