Thanks don_falcone, on a live CD the OS is loaded into ram but I'm not sure what happens when you remove it either. They are not persistant for a reason and any additional software you run is still loaded off the disc. So pulling out a LiveCD mid-use is one thing especially when the applications know that there is no write access and no persistance when they load into ram from a liveCD, suddenly yanking out a HDD however... I'm even less sure at what happens.

I haven't tried pulling out a LiveCD while using it, I'll try that later (I use LiveUSBs since they offer persistence) but I suspected that removing a LiveCD when the OS is running wilI still throw up an error and more than likely prevent the use of any further applications (they are not loaded into ram and reside on the disc only) since you essentially removed the entire filesystem. just as I suspect yanking out a HDD would do even worse. I just didn't know Linux would handle such a failure so gracefully and without warning and wanted to determine whether my HDD was failing or if it was something else. It seems odd to me that Firefox didn't complain about its directories suddenly disappearing, Linux suddenly losing its filesystem, etc.

I'll check the S.M.A.R.T log of the HDD as suggested, I remember my old drive in this cramped case having a few warnings that the temp threshold was exceeded, I'll see how this one is holding up.
I have all my data on a NAS device so I'm not too worried about its failure.