Stupid question: how do you know whether what is in the vial matches the label at all?

You are not imagining it and you are not being difficult. Document it and take the document in.

Followed, this answered three questions I had.

How do you get a clear photo of an imprint? Mine keep coming out blurry. Side effects was my main issue with a small yellow tablet too.

How do you tell the difference between the drug working and just a good week? Not on a concert but the pattern is familiar.