I need my DLC!

So I bought my XBox One and also had the Forza 5 Limited Edition pre-ordered. I got it around Christmas time and automatically started playing it. There were many bugs in the game and on one track it would automatically kick me out of the game. In order to fix this, I had to restart my career. With restarting my career, I lost all of my DLC and Limited Edition cars. Also the Day One cars. I have tried re-using the code but it doesn’t work and I don’t have access to the dlc anymore. Help would appreciate immensely.

Have you looked in download history, if there is one?

Select menu on Forza 5 and manage games. Go to the add ons and reinstall them.