If you think cats don't come when called, you've never seen me yell "Whitey, Dinner!" at supper time. The volume wakes him up, and the associated food preparation noises send him trotting down to the kitchen.
Alas, last night's normalcy ended with his arrival. Whitey sniffed at his bowl, and then he walked away, leaving it untouched. His next stop was the front hall, where he threw up a soft mustard yellow solid (not a hair ball), and then he settled in the living room looking tired and a little tense.
He never did have dinner, although later Katherine got him to take some cat nip both for the tummy settling effect and the happy cat effect.
This morning was better. When I found him in the living room, he got up and comfortably stretched. He later visited Katherine upstairs to tell her it was breakfast time. When breakfast was served, he at least sampled his food. An hour later, he stopped by at the kitchen sink where I was working and gently meowed for some more, which he received and made some more progress on.
He's not back to normal, but as Katherine notes, after stomach trouble she doesn't jump back to full meals either.