I know I posted yesterday on this and tried to be very diplomatic in what I said. Trust me, you don't want to know what I really think about the advise your vet gave you.
Anyway...Im just going to add one more thought onto this thread.
When I had Half-Pint, my dream Yorkie who became ill and my personal vet was out that day so I had to use the other vet that shares his office he told me this.
"Give Half-Pint this drink every half hour. I've kept dogs alive for days on this stuff". Wanna know what happened? Half-Pint died within two hours.
I am sorry, but vet's are human, they are not God. We can put as much trust into them as need be, but if you ever feel like something just don't seem right, find another vet.
Think about it, most humans weight what? 130 - 180 pounds? What would happen if we went 4 days without food? We'd be feeling pretty darn crummy, think about a small little Yorkie. No way is going this long without nutrition going to keep a Yorkie healthy, barely alive, and suffer needlessley.
Follow your heart and your brain when it comes to finding a vet who cares and is truly knowledgable about the Yorkie breed. PLEASE!!!!!