I can think of several reasons.
They might not have that medicine.
The dosage might seem abnormal and he would have to telephone the doctor.
The prescription might have been altered.
The medicine might be a drug that could be abused.
The pharmacist might wonder at female hormones when the presciption had a mans name
Since we sometime use female hormones to treat cancer I doubt that would be the reason. I suspect he was questioning the dosage of the medicine.
I can think of several reasons.
what part of Quietly, With Compassion and Humility did you not get?