I did not receive an activation code for COD:Ghosts (PC). It was not in the case. I live in Iceland and the game was bought in the US for me so I am not in a position to go and exchange it for another one.
Unfortunately it falls onto the retailer to provide a complete version of the game. If for whatever reason a code was not included, you will need to take that up with the retailer from where you purchased the game.