I think the answer is likely no but I said I would ask.
Background: MIL was very trusting of someone she shouldn't have been. An old friend of hers (from years ago) got himself into financial difficulties and MIL took out a second mortgage on her house to help him out. There was no written contract between the two. He moved out of where he was living and in with her (platonically) while she helped him get back on his feet. One day he walked away. He left behind a car with money owing on it - MIL was harassed by some loan-shark type and had to get the car taken away. He left behind various electronic things. Literally, he took what he could carry.
Very soon after this, SIL was in contact with the ex-friend and he promised he would pay back the money (about 50,000 pounds). He said he would put a lien on his property, whatever it took, he would pay it back. We are not positive that he owned that property to begin with. I guess he got used to his new debt-free life and disappeared again. We have no idea where he is or if he's working or anything.
MIL has been to solicitors but they say it is a civil matter because there was no written contract. If she can find him then she can sue him or get his wages docked.
This all happened 5 years ago.
The only info we know is where his mother lives. She is about 70/80 years old now. We're not in the habit of scaring little old ladies, but at the same time, MIL has had a few health and mental issues over the past few years because of what this ex-friend has done. She is forking over 300 pounds per month to cover the interest on the mortgage she took out to discharge his debts.
Is there a way that his mother can be held responsible for his debt? By putting a lien on her house perhaps?
Or, as an alternative, is there a way to find someone that doesn't want to be found?