After not working on a project for a while, my renders disappear

Question

I've been working on a project on and off for a couple months. And this is the 2nd time now that I've left the project for a few weeks. When I come back to it, all my rendered footage is gone.
I'm importing 720p HD footage (.mov) so I need to render everything in order for it to play smoothly in the project. A few small bits of render to remain, such as titles.
This is probably something simple. But could someone clarify what's going on, and if theres something I can do to prevent this.
Thanks

Answer 1

Well I wanted to chalk this up to some kind of mistake on my part (which it probably is). But the renders are definitely disappearing, perhaps not on there own, but without my knowingly doing so.
Here's my guess: my project data gets stored in the default My Documents location of a Windows XP x64 installation. But I have a dualboot with GNU/Linux. While I don't normally use the NTFS partition where the premiere project data is stored, sometimes it does get mounted. After working on a project a couple weeks ago, I just came back to it, only to find that the entire render bar above the timeline is red instead of the green that I had left it when I last worked on the project.
Additionally the directories titled 'Adobe Premiere Pro Preview Files' and 'Media Cache Files' both have a subdirectory with files specific to my project, and those subdirectories are still full of the render data.
So first off, regardless of what may be causing this problem, is there anyway to force Premiere to look at a certain location to re-find the render files?
Second, would my hypothesis of Linux mounting the parition where the Premiere data is saved make sense why the renders 'disappear'? Any other ideas what might be causing this?
Thanks