Not sure if I'm missig a disk from this game. Does anyone know if the game consists of one or two disks?

one disc

I have two jewel cases with different inserts, both identifying them as Lifestream. I have a post-it note on one showing I sent a disk to someone and there is no disk in it or reference to who I sent it to. The second jewel case has an install disk for the game.

I thought that maybe I was missing a disk because of the differing jewel cases. Seems strange.

Maybe you had two copies of the game and loaned one to somebody?
My games is on one disc and came in one jewel case. The jewel case insert is a single piece of paper. It looks like this

http://www.mobygames.com/game/windows/lifestream/cover-art

I misspoke about the second jewel case; it doesn't have an insert. Apparently, when the disk was returned to me I put it in a jewel case apart from the one it belonged in, the one with the inserts you show in the link. Now all I have to do is take it out of the one it's in and put it in the other.

Thanks. Apparently my thinker hasn't caught up with the times yet.