It's quite simple really. Anything that has not been saved does not really exist. It is transient and temporary. It is not data, but the virtual ghost of data.
Anything that has only been saved on one medium (i.e. just to one disk) is semi-permanent. It exists up to the point the disk fails or it gets deleted accidentally.
That is how computers are and always have been. No hardware, software or OS is invulnerable to crashes, bugs or user error.
Save often and backup to different media, often.