If it shows 0 B used/ on disk it's the opposite of being filled up, it shows up as a 0 size disk which is pretty much equivalent to a broken disk.
You can use testdisk which is a free program to scan disks for any kind of data to save on your hard drive, recuva is another free and small tool.
Or just write data recovery software in google and try all of them.
For the most part if Windows is asked to copy data to a USB drive (or any other drive for that matter) and discovers that there is not enough room available then Windows will pop up an error window of some sort. And not "fill to the brim".
Anything you do could cause permanent loss of data.
Before applying any given fix or recovery process knowing what happened may be helpful.
As mentioned above filling the drive completely does not make it UNREADABLE. There might be something happened to the storage drive due to which the drive got failed.
Hope you have backups of your important data. In case you want to recover data from a failed drive you can opt for any data recovery software or service provider but not sure if that helps you recover all your data from the affected storage drive.