Your dad gave an unsecured personal loan, in return for interest. Unsecured loans are inherently risky. Ask your dad how much interest he was charging the friend.
Generally, interest rates for such loans are quite high; anywhere between 18-24% per annum or sometimes more.
The high interest rate is precisely due to higher risk of default; since higher risk demands higher reward.
Now that the friend is insolvent and has defaulted; you have no option but to wait and hope for him to pay you back.