All Premiere Rush projects gone – what to do?

Hi all,

launching Rush today I had to login to my CC-Account. This is not unusual and is known to happen regularly. However, after Rush opened the project library appeard as completely empty. Nothing in there. 

Apart from the fact that something like this shouldn't happen, among other things a 45-minute project file of my daughter's that she had worked on for many, many hours disappeared. 
The project was not synchronised via the cloud (because that seemed absolutely unnecessary).
What can be done? This is a medium disaster for the school project. Since Rush doesn't back up local project files for some unknown reason, all the work seems to be lost despite regular HD-backups.

Something like this should not happen – what is the point of backups then?

Thanks for any ideas.

We are working on a 2020 iMac, running Big Sur – in case this is important.