I think things like this CAN happen, but I am not a vet or an expert at all. What I know of "exposed hardware" is from what I have heard about some human (usually bone) repairs, and have heard of one or two cases among people I have spoken to! -where screws, metal fixings etc have protruded slightly from the skin.
This of course was considered a failure and a corrective surgery had to be scheduled.
I can imagine it is similar in dogs...but in SOME surgeries stabilising fixtures are inserted, which are intended to be removed later by the orthopedic surgeon in a second operation when healing has taken place.
However, I should imagine that would already have been explained to you by the vet/surgeon??
So in the absence of anything like that having been said, I would think immediate examination by a vet (preferably the one who did the surgery) would be advised
I don't honestly know if that is an emergency or not. With no swelling, signs of infection or pain, it is a very odd thing.
I would say the best thing you can do, is take her as soon as possible to get this checked, and maybe don't wait for your scheduled appointment next week.