I think we must take into account that for a long time - several months - this particular brooch was part of the Diamonds display at Buckingham Palace, along with the other major pieces of the Cullinan, which will have put it out of access, not only during that time but probably in the lead-up and run-down too. I'm sure it will be sparkling back on the scene soon.
--Previous Message-- : I did a little research, and according to : another royal jewelry blog I follow, the : last time HM wore this particular brooch was : on March 11, 2013 for the Commonwealth Day : Reception. :