Before you grab the Spirit bear make sure no one else near tries to grab him too. If you grab the bear and someone else starts the quest or tries to grab the bear you will lose yours, even if they are not grouped with you. If you fail, hail Shaman Medicus again to repop the projection.
Using the Sokokar post can work to complete this part. The bear will not be there when you land, but if you go to the ramparts, the quest will still update.
While it is possible to do the quest chain up to this point by speaking to Medicus early on, this last quest in the quest chain will not be available until all previous quests has been done for Lord Scheckt. The quest "Is there a Shaman in the house?" needs to be completed to unlock this quest.