What an enterprising hog taking over the tortoise bed! The hog may have been temporarily grumpy at not finding any food, but it could just as likely have disappeared to hibernate. They normally don’t hibernate in the same place as they have been spending daytimes, but build a special hibernating nest – hibernaculum.
They do tend to arouse from hibernation from time to time for short periods, so it’s worth leaving a small amount of food out – but some hogs also decide not to hibernate at all and stay out and about all winter, in which case just keep feeding as well as providing a constant source of water.
The hog may already have returned, but if not hopefully it will be back after hibernation, if not before.
Good luck and I hope the hog as well as the tortoise have successful hibernation time.