What seems to have happened is, that all of the drums for a single session (project) that were bounced tracks (they were bounced after some edits), for whatever reason, did not get stored in the Audio directory, even with other bounced tracks from all other projects. I certainly cannot explain this, as I don't recall having to specify where they were going, and all of my other bounced tracks were right where they were expected to be.
However, last week I was rebuilding my system after a motherboard failure rendered the last build unuseable, I backed everything up, and restored from the backup. Those bounced tracks were never on the backup, which really bugs me, because they were obviously somewhere, just not in the folder they should have been.
I'm not thinking I didn't make a mistake, but I certainly don't recall specifying a folder where these tracks should have been, and I don't believe I would have been in my right mind to change something like that.
On the new install, I did specify all default locations to be my D drive, which is actually a fairly tedious process.
My main recommendation is that Sonar X2 tries to be smart about where audio is stored. But sometimes that can get you into trouble, if you don't understand what it's doing and why.