Mr Joy said he agreed to pay the settlement in the form of a loan, and that his daughter had vowed to repay him by signing over the house she had inherited into her stepmother Glenda's name.
According to the UK couple's version of events, Lucy promised to pay her parents rent until she had repaid the entire cost of the loan, at which point the house would then be returned to her ownership.
After reaching that alleged verbal agreement, Mr and Mrs Joy remortgaged their three-bedroom home in Cornwall in southwest England to cover Lucy's debt.
A month later, they contacted Lucy to ask when she would sign over the deeds to the house, which she declined to do.
They finally took her to court in 2017 in a last-minute bid to recover their losses, but lost their case this month.
A judge ended up ruling in Lucy's favour after she argued the money had been given as a gift and not a loan.
Mr Joy, a retired British Airways worker, told the Mail on Sunday he had suffered a nervous breakdown as a result of the rift with his daughter, who he has since disowned.
"It wasn't meant to go this way," he said. "You trust your children, don't you? Why would you get them to write an IOU?
"But it's cost us everything. I haven't got a daughter any more.
"I can't get my head around it. When you love your children you can't envisage things would turn sour."
Mrs Joy said her husband was so worried about his finances as a result of the dispute he was now "like a haunted man".
She said her stepdaughter had "turned" after the couple confronted her about signing over the house, and that she regretted not insisting on a written contract.
"She said, 'You're trying to steal my baby's inheritance, screw the pair of you', loaded up her car and drove off," Mrs Joy told the Mail.
"I still have bad nights over the injustice of it all — and our stupidity. I should have said, 'sign something'."
Mr Joy said the couple hadn't spoken to their daughter for months and that he didn't even know if he could bring himself to attend her funeral if she happened to pass away.
"Lucy has got what she deserved. But she didn't deserve to do it at our expense," he said.
"Fighting over a £200,000 house has cost us everything."