Most if not all debts are shown on a credit report unless this debt is some sort of personal loan.
If the loan is neg am, the part he has the refi in 2 years isn’t because it is a neg am, but most likely because that is when his prepayment penalty period is over.
The lender won’t do jack. Depending on how much of a down payment he’s put (if at all), losing his home won’t be because of the lender but from payment hikes and growing loan balance if he’s only been making the minimum payment. In my experience with meeting people who have taken out these loans, everyone without fail will only make the minimum payment.