Do you have a recent save that you can reload and kill Josephine again?

You should be able to pick the staff up using Telekinesis (it is stuck in the bookcase or wall?). Spell books can be bought, or use iZakaroN's SaveEditor (or from Kiya's site, with description) to give yourself a couple skill points to learn it.

Alternately, you can download the inventory files to get another staff;
Lost Items - guide and directory of inventory files


You can into Sir Patrick's treasure room for the deed using;
Teleporting Anywhere, via hex editor