I shut my computer down, and restarted it. When it started back up, my LR5 catalog just disappeared. It reopened to a catalog from last year. I did a search for .lrcat files and found the one catalog I was using, but none of my work/files/anything from the past year was there. I'm a bit baffled by this. How does all the work in a catalog just disappear? Any suggestions?
I don't know how this happened, but you should restore a recent backup copy of your catalog.