Transact SQL :: Query That Returns Material (items) That Are Used In Event On Certain Day - RIGHT JOIN

I have a query that returns material(items) that are used in an event on a certain day.

SELECT C.categoryName, count(I.itemID) AS InMission
from items as I
RIGHT JOIN Categories AS C on I.categoryID = C.categoryID
INNER JOIN LinkMissionItem as LM on I.itemID = LM.itemID
INNER JOIN Missions as M on LM.missionID = M.MissionID
where '2015/12/19' BETWEEN M.freightLeave and M.freightReturn AND isReturned = 0
GROUP BY C.categoryName, C.categoryID
ORDER BY C.categoryID

There are a total of 20 categories and I would like all the categories listed in the result even though there are no items booked in a mission. At the moment, I can only get the categories that have items in that category booked in a mission. I hoped that the RIGHT JOIN on the categories table would do the trick but it doesn't.