You’ll need to run it with administrator privileges: sudo testdisk. With Ubuntu running, install TestDisk using the command sudo apt-get install testdisk. You can use TestDisk as a rescue for Windows or Linux partitions, but you’ll need an Ubuntu live USB drive so you can boot into a separate environment on your PC, and then retrieve the lost files.

(You can delete the data itself too, but usually this requires deliberate deletion with tools like shred.) The deletion just removes the pointer to the data, allowing the the OS to write over those blocks. TestDisk’s website says the program is designed “to help recover lost partitions and/or make non-booting disks bootable again when these symptoms are caused by faulty software: certain types of viruses or human error (such as accidentally deleting a Partition Table).” One thing to understand about storage drives is that when you delete a file or partition table, the data is still on the disk. (It’s also available in the Arch Linux Extra repo.) It turns out it’s in the official Ubuntu repositories that ship with Ubuntu 16.04. It works like a charm, but does so without the aid of a flashy GUI. TestDisk has been around for a while, and was even reviewed by PCWorld in 2011.

After a mild panic attack and several assurances to her that I could fix it, I found the program that saved my butt: TestDisk.

Testdisk kuyhaa