Hey there, I had the same problem. What I did is save the .rtst_vpk in the forlder I wanted it to be in and then just leave it where it is with out any other changes.
If you have already a voice pack .rtst_vpk just place the .ogg files where they were originally and name the folder (where your .ogg are) as it was when you saved the .rtst_vpk
Hope this helps!