2nd Mortgage overlooked when selling house

[Charr66]

My Mother sold her property in 2005 . Somehow when she sold her property the 2nd mortgage was overlooked. She doesn't know how it happened . She had been receiving the bills and paying them till about 3 months ago and she realized that she didn't owe that because it was supposed to be payed off when the house was sold (Please dont ask why she didn't realize before I can't answer that . She says when she gets a bill in the mail she pays it so I really dont know what she was thinking) So anyway apparently the house is in forclosure and my Mother gets a call from the title company who now says they are responsible for this bill and they want my Mother to pay them . We have looked at most of her paperwork on the sale of the house and the 2nd mortgage isn't on any of the papers that we found. Somehow when the title company did the original search it slipped thru the cracks and didnt show that she had a 2nd mortgage . We just dont know what to do . Is she responisble for this money or should she get a lawyer ? She doesn't have any money to give them .