Legal Question in Intellectual Property in California

This is not an intellectual property question, but rather a real property question. That said, you should understand that a Deed of Trust is separate from the Title in real estate. The fact that you transferred title doesn't mean you are no longer obligated under a Deed of Trust. You should have, at the time, discussed this with your lender (and attorney) to make sure the proper paperwork was done to transfer the loan to ex at the same time the title was transferred. That might, however, have meant refinancing the property and going thorugh another closing, with all the fees that involves. You might still be able to do that. The best thing to do is call the lender and ask what their procedures would be. At the very least, you might be able to persuade them to stop reporting this on your credit, given the circumstances.