Why does this Robocopy command make files hidden and how can I unhide them?

Question

I am trying to make a backup to an external HD using Robocopy. I am wondering why it makes the destination directory hidden and subsequently why I can't unhide it? Note: I'm new to the Windows command line. This is the first command I have ever passed.

The command I used is:

Robocopy D:\ I:\destination-directory /E /R:0 /DCOPY:T

The backup worked fine, but it made the destination directory hidden. Then I tried to unhide the directory with the following command:

ATTRIB -H "I:\destination-directory" /S /D

and the output is:

Not resetting system file -- I:\destination-directory

So,

1. Why does this Robocopy command hide the destination directory?
2. What can I do to unhide this directory?

I would like to use the command line to do this.

Answer 1

it may have the system attribute st as well. See @Daniel's command