Hi there. Yes, "Kimi wa inai ka?" means something like "Are you there?" I love that song very much, I think it's a beautiful piece.
This is Toshi's Official Website (in English):
http://www.naturallyart.net/ , you can find full discography there, among other things (interview, lyrics, downloads, etc).
I'm not much into Toshi, btw, I'm just way too obsessed with the whole X to not know about Toshi as well. He was part of it in the end.