I would think the previous promise could be taken as a contract that would entitle his friend to receive half the prize directly?
That would be an interesting case. Arguments against it being a contract would be lack of consideration (this assumes they weren't pooling their money to buy tickets) and lack of a writing (both for evidentiary reasons and as a potential violation of the statute of frauds). His friend's "are you jerking my bobber" statement suggests that the friend didn't view them as having an enforceable contract.