One of the hogs has been turning up really early here too – about 7.20 last night. The problem comes when the clocks change. Dangerous time for the hogs, because we humans start doing things at different times (in hog time), travelling home from work later, etc.
Your theory re. The hog house sounds quite logical. They apparently sometimes move nests during hibernation, so it seems quite likely that they would not use the same nest they used as a day/night nest. Also, not sure they would choose to hibernate near a food source which could attract predators.
Keep a look out, though, because new hoglets were turning up here until late November last year (some after all the adults had disappeared), and they are the ones who really need help with supplementary feeding, etc.