If I recall correctly, Osius has one of the parts of the Psionicle. I think what I'm going to say is that Osius decided to stay behind in the city, to listen for news of other parts of the Psionicle, and gave his part to somebody else for safekeeping. That way, if/when Zhure comes back, Osius is still around...
And speaking of the Gems... though the power setup has been seriously overhauled in 3.5, I think that their abilities still stand (excepting, of course, the mention of 0th-level powers). WotC didn't indicate what discipline the powers in the general psion/wilder listings were part of, so that might be a bit of a problem, but overall I think it'll work. The Gems also grant access to their respective discipline power lists.