Rob was using Adobe Premiere to edit his video, but he ran into problems when his external hard drive gets unplugged. Leo says that if a hard drive suddenly gets disconnected, OS X doesn't like it. Modern operating systems use a journaling setup that will save up a bunch of data before it writes to the hard drive. That's why OS X wants him to eject the drive first before disconnecting. When he disconnects while the hard drive is writing, then the hard drive writes a kind of 'word salad' to the hard drive that could corrupt it. He'll need some recovery software that can fix the file table.