I got this from the official Saints Row Facebook page:
"For Xbox 360 Season Pass Holders, you may need to download the Viewer Pack first, then load up a save in-game that has the first crib unlocked, and that will grant you the new content. Have fun!"
If you go to the Marketplace and download it (it's free) and then load up your game with the dlc, the mission should hopefully be there in your phone.
Hope this helps!