As everyone said, there's just no way to be sure. Different families of humans have different scents, though, so complete speculation says: Maybe your friend smelled different enough that the snake wasn't sure what he was, and warmth and an unfamiliar scent triggered a defensive response.

Unless he bit and wrapped, this probably wasn't about feeding. I have had some baby ball pythons bite me in the fashion you described when they were unhappy with the way they were being handled (posing for photographs). (Rather than a strike, or a bite and wrap, it's more of a 'find a good spot and sink your teeth in, then let go').

Maybe he was just not in the mood, and didn't trust the situation, and wanted to make that clear, lol.
Cats do the same thing--if they've had enough of handling, they may turn and bite. All animals will bite, it's one of the few ways they have of signaling their displeasure.