That's too bad that your daughter didn't get the message about the school closing before she dropped her daughter off. Depending on the age of your granddaughter, it could have been a frightening situation for her.
Hopefully the school figures out how your daughter was missed in the notification process and will have the situation fixed.
Surely she did not just drop her off and drive away. I mean she had to notice when she pulled up that there were no other cars there. Surely she would not just leave a kid at the school with no one there. The way I read it she did not actually drop her off. Just went to the school and then it was closed.
The schools in my area are putting announcements on Facebook. I don't know how else they contact parents if their child is affected. I know people who work in the school system and they say you can not get a parent or guardian to answer the phone. Either no one answers, it is a nonworking number, disconnected, or whatever. Then the parents want to get mad when no one called them. It is not the school's fault if you miss the call or change your number and do not update your info with them. And some people change their ph number like normal people change their socks. I guess trying to avoid bill collectors....