Our 17 year old was like that a couple of times and needed an enema to clear compacted material out of her bowel. She was a long haired cat and did groom herself though we helped with brushing. We had to give sub-Q liquids for a while.
How long did your cat not eat? Did your Vet mention Fatty Liver Disease?
We offered food in tiny, tiny amounts to tempt our girl. Like, 1/8 of a teaspoon at a time. If they are not feeling well a big plate of food is off setting, just as it is for us.
Good luck, let us know how it goes.