I've received an alert from credit agency that I owed 12K?

I have first and 2nd mortgage with Countrywide and they have approved a short sale, escrow closed 792008 with a letter from their Negotiator they will not pursue any deficiency judgements and also received a reconveyance letter that both loans are paid. Now, I received an alert from credit agency stating I owed $12k from BAC Home LNS LP/Countrywide, they have used the account of the 2nd mortgage and I don't understand it. They have put the same address as CW, please advise. Your help is greatly appreciated.