Hi,
the cell manager isn't going to delete the store. That's a bit unintuitive, given it can create both the initial SOS directory structure, and the specific store within that. But it's mostly only associating a B2D device, a bunch of B2D gateways and a backend store - once created, the store itself and the StoreOncelibrary directory it's housed in will remain. The latter can contain more than one store anyway.
So the --delete_store option to SOS will delete a single store from the bunch of stores an installation may house, but it will not remove the entire structure, either. If you are keen to clean up further after getting rid of the B2D pool, gateway and device itself in DP, you would have to delete every single store in the installation (look with --list_stores if there are more), then uninstall the SOS component, and finally you can remove the directory structure.
HTH,
Andre.