Well, he never said that D-Riku was missing either. I guess not all of them had to have been present.
This is a true and fair point.
One way around it would be that - later in the game - we see the only mentioning of Kairi, and it is within the CO Data. Arguably that's where all of Kairi's data was due to complications of Xion and Namine, but there's nothing really in the game to imply this so I'm going with poor writing.
I find it strange that her data was in Castle Oblivion's data. I'm going to chalk this up to poor writing, too.
Sora prefers blondes~ *lickS SoNami and Sora/Alice* alternatively, bright haired people *pats SoRi*
Of the above three pairings, I only support SoRi.