hype and switch
noun phrase
The disappointment that comes from building up desire for something because it’s available, and then being disappointed when it isn’t even though you didn’t originally want it at all.
I’d been jonesin' for a reuben all morning, so I went to the sandwich shop and then saw they had tuna melts - suddenly I really wanted a tuna melt, but it turned out they were out of tuna so I had to get a stupid ol' reuben. What a hype and switch.