"hospitalization" has the connotation that admission of the patient was not necessarily the patient's own choice, but was arranged by family and the family doctor, usually for psychiatric reasons!
You are ringing an ordinary hospital, and talking as if they have admitted a psychiatric patient for treatment, and you want to confirm this.
That is fine. I am sure that it was just your accent. I speak fluent english and i can understand that. I am sure that he does get asked that question alot but people might no use proper english and they might just say " I would like to know if my father is hospitalized there instad of saying you would like to confirm it. If you beed any other help you can message me