I should be on a card in the actual game case along with the manual. You should have a box on the cover of the case that states it is an early purchase with a special code. If not, have fun trying to get it from amazon.
the code in the game is for a different in game item. the op is talking about the code for pre ordering the game that gives you the carbon rally car that is mentioned above. hopefully the codes will be emailed out soon. i think amazon said the earliest to get it was 2 business days after game was shipped. hope that helps.