You'll never find out why you were banned. This happened to me yesterday and Activision told me it says in the policy that they do not disclose the reason for you being banned and they say they don't have access to that information. I did not break any of the rules. When I was allowed back online, my stats and everything was reset to zero, I hope this doesn't happen to you, too.
In-game bans are the product of thorough investigation by Infinity Ward. Penalty is not subject to further review and the grounds of one are not up for debate - all bans are final. We understand that you may be frustrated or confused, but we must lock this thread in accordance with our Community Etiquette & Guidelines here http://community.callofduty.com/thread/200684926
For more information regarding in-game bans, please view the Ghosts Online Code of Conduct here https://support.activision.com/articles/en_US/FAQ/Call-of-Duty-Ghosts-Online-Cod e-of-Conduct/?q=Call+of+Duty%3A+Ghosts+Online+Code+of+Conduct&l=en_US&c=Game_Tit le%3AAll&fs=Search&pn=1