Bigbad - to return to your OP -
My one constant motto in life is - Never upset someone whose co-operation you need.
I completely understand your frustration in your attempts to find some information about your dad's condition and treatment, but as has been advised, pleasant persistence is the way forward here - remember, you need their co-operation and answers, they don't need yours.
Human nature being what it is, staff will respond far better if you are calm and polite, rather than developing a reputation as a 'troublesome relative'.
If your enquiries at ward level are drawing a blank, ask if you can make an appointment to see the doctor in charge of your dad's care - always better than trying to collar a harassed doctor on the hoof.
Good luck x.