This take seems overly skeptical to me. Regardless of truth of the 6,000 calorie claim, that kind of weight loss is extreme in such a short amount of time.
To state the obvious that I hope doesn't need to be said to this audience: a sample size of one tells us exactly nothing. What's saying this one guy one time didn't have a nasty stomach bug?
A crazy claim like this requires some kind of study not just one guy's story.