Poor kitty, I hope he feels better soon.
I think you will be surprised with the results if you can find Carbona Shampoozer. The pet stain version comes in a yellow plastic bottle. The regular version is in a red bottle. Both have a top with a sponge surrounded by a bristle brush. (Be sure to unscrew the top first and remove the inner cap liner...took me a while to figure that one out)
If you can find the pet stain version, the red bottle works as well. You shake the bottle, squeeze out the foam and rub it into the carpet. I usually use an old towel to rub over the carpet. Keep going till the stain is gone. Let it dry, then take an old hairbrush (I like the kind with the metal brush thingys with the little balls on the end)
to separate the rug fibers.
I had a dog with diarrhea and this stuff was the best. I now use it for cat vomit. Why do they always pick the rugs?

My cat heaved up a big pile of food. I was afraid to tackle it for a couple of weeks. It dried out and I was able to easily lift off the dried mess.

Ugh.
No matter how easy lift off might be I couldn't leave it- that's just nasty.

I have great luck with the enzyme cleaners like Nature's Miracle. Get up as much as you can with a dustpan, wet a cloth with NM, and scrub up what you can. Then just saturate the area and let it sit. If at all possible I place a folded up towel underneath the rug so the moisture has somewhere to go. Next day scrub it with a cloth saturated in the stuff and everything is magically gone. Vacuum to help restore the fibers.

If the rug is not too unweildy I would take it outside and flip it over and do the same thing- that way you aren't working the mess through the rug.
Either way you need enzymes to break down and neutralize the odor so the pet isn't reattracted to the area.

Thanks to all for the responses. I couldn't find the Carbona cleaner but will order some from Amazon. I did let(what I couldn't scrape up) it dry for a couple of hours.....it was way too runny. Then I washed it and followed up with carpet cleaner and lots of towels. It is a room size rug so I can't take it outside but I will follow up with enzymes. I hope it doesn't ever happen again!

Yes, Cearbhill, I know what I did was nasty and dusgusting. Luckily the cat vomitted in a corner of a little-used room. I was afarid to even go in that room for a week. I just got lucky,what happened was I finally gritted my teeth and went in there and cleaned it all up. I am NOT recommending this method.

Nature's Miracle works lots better than carbona....try it...avaliable at your pet store.
Linda C

lindac, I agree that Nature's Miracle is a good product. I do use it. It is superior to remove pet urine from places it should not be. The original poster said the cat diarrhea landed on the cream colored part of her rug. I have been using Carbona for about 20 yrs, if not more, to remove all sorts of stains from rugs, upholstery and car seats. I have never found a better product for stains.

I have 2 cats. I have a hoover steam vac jr....This doesn't happen very often at all, but a couple of times it has happened on my carpet; I got very hot water and Listerine and and just a tiny bit of antibacterial soap and it came up great. I then rinsed it.