Generally the statute of limitations for most debts in California is four years. In addition, debt collectors are not supposed to sell collection accounts that were the result of identity theft.
I would suggest you contact a consumer law attorney to find out if the collection agency has broken the law. You are in luck - our coauthor Robert Brennan is a California attorney with expertise in debt collection, credit reporting and identity theft laws. You can learn more about him, and get is contact information, at BrennanLaw.com.