Recovering a confused partition table?
Alright, I fixed it. I installed a Live image to my flash drive and copied the TestDisk software to it. My live image was Windows 10 To Go, but I believe any OS could handle it. 

Then, I ran a scan using TestDisk, and re-enabled the "deleted" partitions. After doing this, I wrote the new GPT to disk, and rebooted. Held the option key, and the partitions showed back up.

I essentially followed this guide, but since my partitions weren't actually in the partition table, it showed them as 'deleted' - setting them back to 'primary' and writing it fixed it.

Moral of the story - Don't mess with any partitions on a Mac from anything else than software in OS X or you may trash your partition table.