Apparently the smell comes from butyric acid produced when food starts to break down in the digestive tract. I'd try something alkaline, like bicarb sprinkled on the rug for a few hours then vacuumed up.
I got a spray from pet shop for animal urine and vomit. Used it on car seat and upholstery when DD memorably hurled everywhere. Neutralised smell in car completely, which is pretty amazing when you think of how a smell of sick normally lingers in a car.
Cat litter is great at absorbing bad sick smells. Pour over, leave overnight and hoover up in the morning. DD is very car sick every bleedin' journey and it is the only thing that makes the car bearable.