There is no way to check that. Since the money goes from one player to another, its another player’s responsibility to check background before giving loans. While giving loans, it shows players old loans, how many payments he have missed etc.
If the player doesnt fly in, there is no way to recover the loan.
The whole idea behind the loan system was RP based. Since the money is not spawned in, the economy of the server is not hampered at all. I mean you can make the same case for loans which are spawned money and not player based.
What if player A takes a loan and send the money to his friend and doesnt fly in to pay the loan ever. This way the money is added to economy and not going out of the economy ever. Atleast in the loan system in the banking system, the money is going from 1 player to another and not spawned.