tricky one
depends on the program and how the partition has been hidden.
Some are hidden by a routine in the drives firmware which reduces the size of the drive thats visible to the operating system by loading a false MBR.
When you run recovery, the "real" MBR is loaded, making the partition visible.
However there are several ways of doing this, and some are easier to find than others. The simple answer is until you try, you don't know