I DO know what bitcoin is, and I don't understand how he could possibly fund his trip with it. Doesn't seem like the top of the list for liquid assets, i.e. what you need when travelling. Part of their job is to make sure you can fund your trip. This guy couldn't, from a variety of reasonable interpretations.
Please take into account that this is a kind of story that the agents hear all the time. "Really, officer, I've got this cousin who owes me 3 grand and has the cash ready." To them it doesn't matter that the famous(#) Bitcoin is involved here.
(#) Among techies only and even here the discussions about it being a Ponzi scheme are lively.
You genuinely don't understand how he could possibly fund his trip with bitcoins?
Or are you exaggerating to make a point?
I think it is conceivable that he could fund his trip by bartering for the majority of his food and/or lodging using bitcoins. That is, it is a possibility that there are people in the United States who will accept bitcoins in return for providing food and/or lodging. And presumably as a "digital currency guru" he would be able to identify those people and effect payment with the agreed upon medium.
He even has a fallback option of cash if there is something he cannot acquire through the use of this bitcoins.
Indeed, I exaggerate a bit. But I think @praptak above expresses the issue admirably. It's not a question of possibility so much as one of trust, and it's a customs agent's job to be wary.
