Remember, there is a difference between Sounds and Samples.
A Sample is the actual waveform, a Sound is a collection of all the parameters and Sample of what you customized.
You can create your own Sounds by loading a Sample and tweaking it to taste and then hit [FUNC] + Pattern(Imp/Exp).
Export Sound and select a slot. This Sound is now stored in the +Drive that keep whining about being empty.
Add some tags for easy access later.
So the +Drive has no Sounds by default, but the +Drive does have Samples.