Sorry to hear the hogs there have been missing. Hopefully some of them may have returned by now, but if not, they do tend to go missing from time to time for all sorts of reasons – usually impossible to know why in any particular case. I would continue offering food and especially water, which is best left out all day every day including winter. Either the original hogs or some others may turn up. Hoglets, in particular, sometimes appear quite late in the year and would likely welcome some food.