Let's assume that had she not been given the amnesic medicine, we would agree that she experienced terror when the scalpel approached her eye. The question then becomes: why should the administration of the amnesic medicine change our view? Given your description of the medicine, it does not cause her not to have an experience; it just causes her to forget her experience. So, to answer your question, yes, she was terrified. She had an experience of terror, and she is now unable to recall that prior experience of terror.

You seem to be assuming that we must be able to remember an experience in order for it to have been truly experienced. I am inclined to deny this assumption. To help see why we should deny the assumption, consider a slightly different case. Suppose someone has an instant of terror and then dies. Would you want to deny that she experienced the terror, even though (due to her death) she never was able to form a memory of the terror?

I concur with Amy. We suppose that the eye operation itself took place, even th0ugh the patient forgot about it afterwards. It is natural to suppose that normally, in these cases, the experience of terror takes place at a specific time during the operation. So it is natural to suppose that the experience took place and was forgotten, just as the operation itself took place and was forgotten.

One unlikely alternative would be to allow for some sort of weird backward causation, whereby events that occur at one time can be undone by later events. Another, slightly less whacky, alternative would be to suppose that the properties of a person's experience at a given time are not fully determined by events that take place at that time, but rather are partly determined by their place in the overall pattern of the person's life.

How do any of us know that we haven't been similarly terrified? In typical cases in which an amnesic drug is administered, the subject will remember enough about previous and subsequent events to know that that had happened. However there might be exceptions. So I guess you'd only know for sure if you had a very detailed knowledge of your history.

I am due to have part of my right knee cap surgically removed, under general anaesthetic. There is a phenomenon called 'anaesthetic awareness', wherein the patient is paralysed but remains perfectly conscious. Apparently this is known to happen in about 1 in a 1000 cases. However I have heard it rumoured that amnesic drugs are standardly administered along with anaesthetics. So perhaps the incidence is higher. Should I be afraid?