It may be that when you entered disk management it prompted to "initialize" the xbox drive. This will happen if Windows doesn't recognize the partition table type, such as when you have a Mac or linux disk connected, because these don't use an MBR partition table but just a GPT one. If you definitely didn't format it, you may be able to restore the GPT partition table using a program called TestDisk from CG security to scan the drive, find the partitions, and rewrite the GPT tables.
So I had a 1tb Sea gate drive plugged into my xbox one. I have no memory of formatting it but I'm assuming I had to when I plugged it in for the first time. I decided to add a wallpaper to the back so I plugged it into my computer with Windows 10. I couldn't figure out how to save stuff to my Sea gate drive so I went to computer management > storage > disk management and went to (C:) and went to "change drive letter and paths", I then went to "add", and made a folder called (C:) /xbox usb. I put the photos in this file and went to plug the drive back into my xbox, now my xbox will not recognize the drive and I've lost almost half my games. After plugging it back into my computer, it seems as if (C:) had nothing to do with my sea gate drive, however my sea gate is still not showing up on the xbox. Any suggestions?