NIV, the only contract that we know exists is the one between Ignorantwithlaw and his friend.
There has been no indication given that the friend's father was a party to this agreement. In fact, the friend's father may have no knowledge at all of the agreement.
I agree that there could be all sorts of other facts that can be added to change this but, as it stands, the only one Ignorantwithlaw can sue for the return of his money is his friend.
What "agreement" are we suing on again? Has it been breached? If we are going to dismiss reasonable assumptions because they are not stated in the question's facts, I don't know we have a contract with the the friend. (Which is why I suggest the suit be for conversion and not a breach of contract. Even then, that's just a guess.) LOTS of facts would need to be known about this, starting as to what has happened.
1. Were OP and friend talking and friend offer to sell a widget to OP. OP, knowing friend's father makes widgets believes it will come from father and agrees.
is different from;
2. OP comes up to friend and father and offers to buy widget from father. Later gives check to friend to pay for widget and complete the deal as friend mentions he will see father later.
I agree that WHAT happened is essential to understanding the legalities of the situation. I don't agree the bringing up of the only issue the OP asked about is improper just because some reasonable assumption must be made to get there, especially when we have no idea as to if any potential contract/agreement has been breached without a few assumptions as well.