You will see it on the counter first. A glass dish with masking tape on the bottom and a name written in marker, or a foil pan with a lid from the grocery store, sitting where somebody set it down weeks ago. Maybe there are four of them. The lasagna pan, the bread pan, a plastic tub of soup nobody has opened. Each one came with a neighbor or a cousin at the door, and each one has a return address you could walk to in ten minutes.
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In the first months, nobody expects dishes to go back. Your mother would have had them washed and on the neighbor's porch by the next day, with a note in her handwriting. Your father is not doing that, and that is the thing you are noticing. A dish sitting is not a crisis by itself. It is a small signal that the thank-you part of the visit has stopped, and when that part stops, the visits often thin out too.
What to check tonight
Walk to the counter and count. Write it on the back of an envelope if that helps: which dish, whose name is on it, whether it is still full, and whether the food in it has gone into the fridge. Note which ones have been sitting the longest. Anything with food that has been out for days should be thrown out and the dish washed, and you can do that without making a fuss about it.
Then look at the rest of the room for the same pattern. Is the mail stacked the way it was? Are the blank cards still in the box? Is there a pile of thank-you notes he meant to write? You do not need to fix any of it tonight. You are only getting a count, which is the thing your mother kept in her head without thinking about it.
What to do this week
Pick one dish and take it back with him. Ask him to come to the neighbor's door with you, or offer to drop it off on the way somewhere. Keep the errand small. Say something plain, such as that the neighbor asked about her pan, and let him decide how much to say at the door.
If he says no, do not argue about the dish. Take it yourself, thank the neighbor on his behalf, and write down who came to the door. The point is that someone outside the house is still in the loop, and that the neighbor gets an answer instead of silence.
Offer to write the thank-you notes with him. Sit at the table with the box of cards and let him say two lines out loud while you write. His own words often come back when he is talking, not when he is staring at a blank card. Keep the list short, three people at most in one sitting.
Signs it is more than a slow week
Watch for dishes stacking up over several weeks while the visits themselves keep coming, or for him no longer answering the door at all. Watch for neighbors who used to bring things quietly stopping. Watch for a fridge that has nothing in it except what people brought. Those are the signs that the thank-you stage was not the only thing going quiet.
When to ask the doctor
Bring it up with his doctor if he seems to have lost interest in food, sleep, or the people who used to come by, or if the quiet has lasted long enough that the house is showing it. You can say it plainly: the dishes are not coming back, he is eating less, and he has stopped going to the door. Those are observations, not a diagnosis, and the doctor can ask him the questions you cannot. Write down what you saw and when, so the visit has something specific to work with.
Good-week card: the dishes went back, and a neighbor got an answer at the door.