Ruined Surprise!

My husband and I decided not to find out the gender of our baby but now for the third time, a professional (nurses and doctor) have called the baby a "he". The last one, the doctor walked in said how's he doing ...he or she? Do you know? Is it possible they don't know? We had the 20 week sono at the hospital but I assume the results were sent to them and is in my folder. 😔