Trying to clear 2nd mortgage from the title

Hello,
I am real estate agent helping a client. My client had 2 mortgages on her home. She filed Chapter 7 BK in 2009. She stopped paying the 2nd mortgage after the BK discharge. I obtained the credit reports from Transunion and Experian. The 2nd mortgage is reported as Charge Off account as of July 2009. Balance $0. Last reported 07/2009.
I called the creditor PNC Bank to negotiate this account. PNC Bank could not locate the account by Social Security Number or the account number. So my best guess is that this account has been sold to collection agency right around July 2009. However PNC Bank doesnt have any information about this account and to who it was sold. I combed through 2 credit reports and did not find any other creditor reporting this account. I understand that its against the law to collect on it due to the BK protection. The lien is still on the title of my client's home. The only way to remove this lien is by locating current creditor and settling the account. My big question is how can I locate the owner of this account or is there another way of clearing the title of the home?
Thank you very much in advance!