Originally Posted by: RogerTheAtheist 
Based on what I'm seeing online, the DLC was removed less than four months after the season pass was on sale. I guess most buyers would've already had the game, but there was no warning that I remember saying that it would be removed shortly.
Don't mean to dig up an old grave, it's kind of recent anyway. Today I wanted to revisit FM4 and I was looking for an answer regarding the SP.... but then found an answer on my own.
So I found out if you own the SP, and also have the free-cars in your download history. The key to those packs as a SP owner is actually just the free car. Download the free car again and you're fine. Example the 2011 Mazda RX8 R3 was the December IGN pack itself. If you don't have the free cars the SP is a total loss for you.