Erosion and Aground are maps designed specifically for Face Off and are free to the public. Other Face Off content is available in MW3's Collection 2 and Collection 3: Chaos Pack downloadable content packs. These are available for 1200MSP each via the Xbox LIVE Marketplace.
Then something may be wrong with your dlc. There should be more maps then that. Trying going to the store and having it isntall all the dlc agian to make sure nothing is wrong. Other than that I have no idea really.
You might have to delete it all off the hd first, then have it reinstall fresh, could take some time with as many as there is. but could solve the problem. or at least delete the FO maps that were part of each dlc then have it re install those maps.