It may be unusual, in that it isn’t what the average hog does, but with changing weather patterns, etc. as well as hog individuality, mabe not surprising. It may be that the hog hadn’t put on sufficient fat to survive for longer. Another possibility is that hogs do emerge during hibernation and sometimes even change nesting sites, so it may have done that and just decided not to go back into hibernation. It’s a lucky hog that you were there ready with food and water!
Good luck. I hope the hog does well.