[Whewt22]

Kisuke was working with Mayuri not Aizen, and Rukia wasn't apart of the gotei 13 yet. He had to take the Vizard to Earth, to finish working on them, so he obviously took the hogyoku with him there.
Ichigo has an inner hollow due to the fact that he was able to resist transformation, and become a shinigami instead. Im thinking that obtaining Shinigami powers while obtaining hollow at the same time, is sort of like a natural hogyoku.
But yes, Aizen finally figured out where Kisue was hiding it, and did everything he could to get it. He did, and the newest espada, are created by the hogyoku.