How do I fix missing clips
Last night I was worked on a video segment and everything was fine. Today I came into work and played my FCP project, and now there are two compound clips that are nothing but blackness and silence. I went inside the compound clips and it shows "(missing)" for the clip names. I can see that the media files are not missing though. Everything is where it's supposed to be -- all in one library file on one hard drive. I haven't changed anything since last night.
I could just re-edit those sections again, but that would be time-consuming, and I don't want to duplicate my work when I have no way of knowing if the same thing might happen again. I tried going to File -> Relink Files... but nothing appears in the "Original files" list, and all the buttons are greyed out.
I would like to make FCP find the "missing" media, but barring that, I would at least like to know how to prevent this from happening in the future.
Mac Pro, OS X Yosemite (10.10.2), 3.5 GHz 6-Core Intel, 16 GBram