Ordering a glass of wine and receiving a different one....How often does it happen?

[rain4st]

HI everyone, Just finished dinner at a local restaurant. Thought I would try a Rodney Strong Cabernet. Had never tasted it before, however was told it was a decent wine. I was less than impressed when it arrived, extremely flat, no body lacking quality. So I proceeded to surmise that A. it had been open too long or B. this was not the Rodney Strong Cab. I proceeded to order Trinchero Merlot that was was rich in blackberry essence and toasted oak finish. I pondered to ask the question on the first choice and finally asked the server if the first Rodney Strong Cab had been open for a while accounting for the loss in flavor. The server went back to the bartender and found out that he had poured the Rodney Strong Merlot and said"he wasn't even aware there was a Cabernet by Rodney Strong"! I truly believe that the merlot must have been opened for awhile as the flavor had all but gone.
The whole point to this is I wonder how often this happens. I am certain often. Certainly this separates a good restaurant from poor one, but I sincerely bet it is a frequent event. Would love to hear your thoughts....