Cat will not start

I borrowed my sister's car which is a smart car, 2004. When I switched the car off, I left the radio and the fan turned on. The radio stopped playing when the ignition was off and the fan stopped blowing, but they were on when I turned the car off. When we have gone to use the car again it won't start and she has said it is because I have left these appliances turned on and so I wanted to check if this would drain the battery as I do this in my own car all the time but have never had a problem.
I'd like to add that she leaves the car unused for long periods and would have thought that was the reason that it won't start. Can you please confirm? Do I need to start turning every appliance in a car off when I turn the ignition off?

Thanks very much for your help.