"Blood test at home"

I got a blood test at home.  I have arthritis (need two new hips) and osteo spinal fractures.  Had I been upstairs/asleep or in the loo then I would have missed the nurse. 

My question is this, why was this so random, no appointment, or even prior notice of the day they were coming? I actually hadn't been informed this was happening so knew nothing about it, although I was very relieved and thankful that it did.  Surely this cannot be common practice? If it is, how many missed appointments (a loose term) were missed or had to be rearranged because no one knew the nurse was coming?

Some sort of booking system must surely be in place but staff seem to be reliant upon a person being home at random without checking in advance, my friend takes me food shopping so I could also have been on my once a week food shop which would have meant wasting the valuable time of the community nurse, which worries me. 

Furthermore I worry that if the nurse comes when my friend takes me food shopping then my elderly mother will not hear the door and that will be an added worry.