I think you may be right in supposing that the Queen Mother's jewels were always in the Clarence House vaults, and probably have remained there, no doubt after auditing. That strange picture of the man wearing the lotus tiara suggests that it lived with the Queen Mother.
There was a suggestion in the press that Catherine had a choice of three tiaras for her wedding. Now that she has worn two, I wonder what the third might have been. Probably not the turquoise.