Cool!!! You are making progress.

I did not play with sub directories much, I was just writing file to the root directory. But I do remember trying it.

Are you using the Extended Command Set with your firmware?

Looking at the
Vinculum Firmware User Manual
Version: 2.3
Issue Date: 2007-12-03

On page 30 section 6.2.1 Directory (DIR)
This statement is made:
Note that if the specified file is a directory, a size of zero will be displayed rather than a listing of the files in that directory.
So maybe you are there and do not know it???