Due to quick CT scanning in hospital - tests for iscemic stroke often come back negative. Stroke can therefore be a "clinical" diagnosis ie the history and symptoms. Sometimes though a consultant may do an MRI scan and that will be pretty conclusive of stroke.
I would say that getting to hospital quickly was an excellent move by your friend as even people with parkinson's can have a stroke. A stroke being a "sudden loss" of movement, speech or sensation. PD symptoms progress slowly. With PD patients the admission to a hospital as "maybe stroke", is often for urine/chest infection that makes existing symptoms worse - hence they are initially felt to be a stroke. Better to get it checked out though, as I said just because you/we have pd dosen't mean we cant have a stroke!
Peanut, this doesn't help on your diagnosis but a discharge letter should go to your GP, and be in your medical notes. do you have a pd nurse who can check? ring the consultant's secretary to get a copy of the discharge letter? It is important that you know if you did or not as you need to be aware of how to try and prevent another stroke! - medication, exercise, weight, etc.
Hopefully your arm has recovered, and you can get an answer soon.