Sounds like a typically perverse hog! Especially when there are some lovely clean huts nearby! I sometimes find them spending the day in my feed box, too, but they normally only stay a day or two. I usually manage to carefully extract the food bowl and the hogs usually do venture out during the night – presumably after claiming first-comer privilege to the new food!
Once the hog has vacated, I would make sure you give the box a good clean (using boiling water if it’s wooden) as if they are sleeping there, they could leave behind some ticks or parasite eggs.