From Cannon Fodder's post:
"I've got Nuketown Zombies from the season pass. Wat u do is install the season pass, go back to the psn store, go to search, type in black ops 2, scroll down to add ons and Nuketown zombies will be there for free."
This was the solution for my install. I was having the exact same issue. Bought the add on and could not find the map afer the install. It is a big file. Took 30 minutes to download over my DSL connection.
Thanks for the tip.
And in the end keep doing it for every DLC if you have season pass.