Easy. Track them down and treat it like any other defaulted loan.
They need to be held accountable.
Two of my kids needed FAFSA loans. One is done paying it back and the other is in process.
My son payed his back with his signing bonus and gave the rest of his bonus to us to cover our side of the loan. His older sister is holding down 2 part-time jobs (thanks Obamacare) and will need another 10 years, or, on the other hand, just a few after Obamacare is repealed.