So what can you do? Luckily, Authorea stores every change to your articles to a Git repository. So, if you accidentally deleted a file, navigate to the History view (from the article toolbar) and select from the History sidebar a version of the article at the time at which your file/content was still present. Click the revert button to revert to that specific version.
You should now restore exactly that version of the article prior to the data loss.
Published on: 12 / 12 / 2017