missing files after processing

just wondering if it is just me, or anyone had the following issue: using CO 4 PRO (on a mac book pro running 10.5.5) to sort, rate and process images. following day all the once processed (including 2-3 variations per image are missing from the original folder! it seems the file went to it's original version as downloaded(even the rating is gone) even starnger, they are still inside processed history, and no problems reprocessing them... so they must be somewhere, right? been using CO for many years without any major issues ever.