Danny left his laptop on while flying and when he went to open the laptop, the drive disappeared and he doesn't know what happened. Leo says it sounds like the drive had been jostled to the point that the computer couldn't read it. It could still be connected, though. It's likely that the disk catalog was damaged or corrupted. He could run disk utility, but Leo isn't all that confident that it will work for him. Drive Rescue could perhaps fix the problem. Disk Warrior is another. He could also take out the drive and connect it to a Windows machine with a universal drive connector and get the data off it. Then he can format it and reinstall everything. Just because it failed, doesn't mean the drive is bad.
Danny also has a 2009 Mac Pro, but Boot Camp won't allow him to install Windows 10 — only Windows 8.1. Leo says Danny needs to upgrade to Yosemite in order to run Windows 10 because it has the Windows 10 drivers.