Advice on Problems with HUD

Hello. My husband purchased a home in Prince George's County Maryland in 1996. A few years later he was injured on his job and was unable to go back to work for awhile. In the process of recuperating, he fell behind on his mortgage payments. In August of 1999 he obtained a loan from HUD which became a second mortgage on the house which was to be paid in full by August 1, 2026. My husband was still not able to return to work, and could not keep up the payments on the mortgage and began to receive notices about his house going into foreclosure. He sold the house in the fall of 2002. The owner is currently in the house. In September of 2007 my husband receives a letter from a collection agency of some money owed. He called to find out it was money owed to HUD. My husband told them that all of that was taken care of at the sale of the house. We recently found a letter that was signed and notarized by the current owner of the house and by the title company that they used to purchase the house that stated that the owner was fully aware that Countrywide Home Loans recorded a second trust in the amount of $9,891.00 on August 19, 1999 and the security instrument was given to HUD with the case number stated. The title company claimed in the letter that Countrywide nor HUD had any recollection or record of a note or requirement for repayment for that amount. The letter ended that the owner that bought the house relieved the title company of all liability relating to this matter and that they (current owner of house now) would be liable for any and all fees related to this situation. My husband filed for taxes in 2007 and his tax rebate and stimulus was garnished by HUD. I called HUD and faxed both HUD and the collection agency the notarized letter and stating that he was not responsible for this debt. HUD claimed that they didn't have any contract with the new owner so they couldn't collect from the current owner of the house. I did find out later that they did in fact contact the current owner and gave her 65 days to pay the loan. She could not pay it, did not deny she owed the money, and they put a lien on her house for the amount owed on the loan. My husband recently received another letter from a different collection agency saying that he owed the money. I sent the same documentation over to them, and they sent me a letter stating that HUD cannot legally collect from the current owner because they do not have a contract with them, so my husband is responsible for the debt. Mind you, this house was sold in 2002, and we find out about this 5 years later. Not only that, how can the title be transferred in her name if a debt is still owed on the house, and how can HUD take this loan in my husband's name and put the lien on the current owner's house? Is my husband liable if we have this notarized letter stating that she is liable for this loan? I don't know what action to take. We have to get ready to file again, and I don't want them to garnish our money. Thanks for your time.