I have a USB HDD that it was working normally.
I've deleted a lot of files. Then I remove the USB (in a unsafe way) and then it stopped showing in Finder.
When I try to open Disk Utility, it loads forever.
When I remove remove the USB cable and plug again, it show my HDD, but like it's empty:
When I run "First Aid", it shows me this error:
I'm using El Capitan.
Maybe i've deleted some files that helps the HD to mount as well