I mean, they did cut the dog open. Why wouldn't they charge her?
Because the surgery was based on a misdiagnosis?
I'm not trying to be obtuse here, but: THEY STILL DID THE SURGERY!
If they diagnose me with a disease and I go buy the medicine for it and later its determined I never had the disease, I don't get to return the medicine.
right, because you've just involved a third party: the pharmacy.
if a doctor told you to take a medication, and he sold the pills to you directly, then later called to say "woops, i accidentally looked at someone else's chart, you don't need that medicine" - wouldn't you be having a chat with that doctor about getting your money back for the unneeded meds he sold you? i certainly would.