Really good news the hog is back. Yes, they do sometimes disappear for no apparent reason and there are always lots of worried people on the forum at this time of year.
Possible reasons are:
Female having hoglets.
Someone else started feeding.
Their route to your garden has been blocked and it may take them a while to find a way round.
Males have larger ranges than females, so may have been visiting another part.
If you keep leaving the food out hopefully the hogs return, as you have found.
Re. eating less food. Again many possible reasons – more food in the ‘wild’, someone else feeding, etc.
If I were you, I would leave some water outside the feeding box as well. I have water sources in several places in the garden all day, every day, just in case a dehydrated hog is desperate for a drink during the day.