My Catalog has disappeared in LR5.  How can I restore it?

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?