cgsecurity.org

I have a 3TB WD Passport Drive. Yesterday I plugged it in and Disk Management showed it as unallocated.

So I ran testdisk to rebuild the BS. It did. But the weird thing was that the drive still showed as unallocated.

Then (probably stupidly), I ran chkdsk /f on it. All of my files and folders appear, but probably 50% of them show as 0KB.

But now, Disk Management shows one partition of 2048GB and another at 1677.99GB that is unallocated.

My drive initially had about 800GB left of free space.

Question is... is there anything I can do to get these files back, or am I just hosed?

Try TestDisk, Advanced, Undelete.
If you do not recover your files this way, use PhotoRec. It will not recover the original filenames but it should recover your data. (You may have to use [Whole] instead of [Free]).
Note that you need a lot of free space to store the recovered files and it must be on another disk, at least on another partition than the source.