Sora couldn't remember Riku from Castle Oblivion, though. (or the replica)
Namine said that when she put his old memories back together, she would have to break the links of the memories in Castle Oblivion, and he would forget everything that happened in the castle.
About that piture, it has been translated 2 different ways. I think KHU was the first to translate it, and they said, "So it was you, Riku, after all." I think kh2.net translated it as, "So it was Riku after all!" I hope it's the first one. I really want Sora and Riku to meet each other again. ^_~