I totally forgot I'd asked a question here! I've never done it before.
But anyway, I ended up solving the problem on my own. I could tell by the dog's body language that the not eating was purely because he missed his family too much to do so. But luckily for me, his family had some meatballs in the fridge that they specifically told me to give to him everyday before they left, so I thought "Hey, I haven't given him his meatballs today!" so I broke them into pieces and buried them in his food, and so he ate all of it trying to get at them, so, problem solved!
He seems to be a bit more comfortable today, so let's see if he eats without a fuss today.
At first, I thought it was medical, because he's an elderly dog with itching problems and an ear infection, but after closely monitoring him for a while, I determined it was all emotional. But yeah, he seems better today, so that's good. He actually slept at the foot of the bed last night, something he hadn't done the night before, so that's a good sign that he's getting more comfortable being around me.