I have come to this late, I know but there is nothing shocking about leaving a responsible 9 yr old on their own.
It is shocking not to be letting a secondary school pupil have any independence. I fully expect my 8.5 yr old to be getting himself to and from school when he is 11 and I can't expect him to be able to do that without giving him increasing amounts of responsibility in the mean time. Refusing to leave a 12 or 13 yr old home alone is amazing!
Really, you can get yourself wound up about all sorts of things that could happen to your child whilst you are out but a 9 yr old should be able to keep themselves safe if they have a set of rules to follow. So don't open the door, don't answer the phone unless you know who it is, don't use the kitchen etc, leave if there is a fire.
I left DS1 by himself 2 weeks ago. He wasn't well - he had tonsilitis. I didn't leave him the day he was in bed and bearly able to lift his head but the following days, when he was too ill for school but upright and capable of sitting on the sofa watching telly I left him to go and get DS2 from school.
He could get out of the front door if he needed to, nobody could get in. He didn't want to go - better to stay at home than getting dressed up to go out when he wasn't feeling well. I was 10 minutes most of the time but one day I was talking to a friend and was 20 minutes. He wasn't in the slightest bit bothered. I am pleased about that - what is the point of making a child scared without need.
FWIW I left for 2 hours a day for a week when I had chickenpox as a child, aged 9 and loved it. I walked to school alone and went to the shops for my parents from age 7. I was even out on the playing fields next to our house at 5 for half an hour at a time. I feel guilty that I don't trust DS1 to do those things although it is more that the opportunity doesn't arise which is sad.