You can try retrieving this hidden folder with the Terminal.
A lot of people aren't aware that the Trash folder is actually located in their home folder.But we know,so we simply navigate there using
Now we list the content of this directory with
You should now be able to see the contents of your Trash folder,including your lost hidden folder.With the next line, we copy this folder to
cp .<hiddenfolder_name> ~/Save/
Note that "~" is like a shortcut to your home directory,it's in fact the same as
Now on the problem that the Trash folder only shows up when your data drive is mounted:
I suspect that the data drive contains your
/home/ folder, and seeing as the Trash folder is located in your home, it is not visible until your home folder is mounted.
The location of the Trash folder may vary on the huge variety of distros,you may have to look it up for your distro in case the one I named doesn't work for you.From the question itself I can't really tell wether your home folder is on the data drive, so if this isn't the case it would propably help to solve your problem if you could provide this info. I hope this helps you retriveing your hidden folder...May the force be with you!