"How do I know this is the same gryphon you ate?"

While Hialfi is best known as a mailman, running a circuit of the Five Villages district six days a week, he has a secondary role as a monster hunter. A two ton foxtaur burns a lot of calories trotting down roads all day, and if he can catch something on his rounds that's less food he'll need to buy.

In this case he caught a gryphon, probably by throwing bolas at it, and said gryphon turned out to have a bounty on it due to its habit of raiding farms and eating sheep. Odds are Hialfi wrapped it up in the bolas cords and swallowed it whole, as it's faster than cooking it. The rubber weights at the end of the cords are indigestible and he re-uses them when they show up later.

There is a whole clan of gryphons on the mountain in the middle of the Five Villages and the patriarch of the clan often sends problem children, mostly the males who might eventually challenge his leadership, into intentionally dangerous situations because you only need so many young lionbirds. At least two have been eaten by Quozl the couatl and at least two by Hialfi.