My meal always disappears automatically when I exit the game. It's never there when I return ...
I wish that would work at my house! Just leave the property when I'm done eating, and return to the kitchen to find it all cleaned up!

In my games, I do a combination of dropping and praising to train them to clean up. After a while, they do it on their own.
Now, if only I could convince my real-life family to do it with just a piece of candy and a few words of praise... 