I am working on a video edit of a 4.5 hr conference and this is the 4th time it has "unlinked" or "lost" the media. The first time, I had to start over. The second and third time I was able to relink with no problem but the fourth time I relinked the media it has erased all of the hours of editing I did. This is extremely frustrating. Is there a way to recover everything I have done?? There is no way I am going to be able to re-edit everything and submit it on time.
How, or where, are you storing your footage? I think that's the first problem you need to solve.
Next, look for your Auto-Save folder that should be in the same folder are your project file (.prproj) is. In there you can find your most recent auto-saved files, assuming you have auto-save turned on in your preferences.