I was working on a cloud-hosted file when Illustrator crashed. I submitted a crash report but didn't get the pop-up to relaunch the app with recovered files. When I re-opened the file, all my work is gone and there are just blank artboards and no objects. It says it was last backed up 5 hours ago, but even then there was work in the file so I can't understand why it's all blank. Can anyone explain why this happened so I can avoid it in future? I was under the impression that cloud back-ups were quite secure?