I haven't been into Lightroom for quite a few months and upon opening it tonight my catalogs & images are nowhere to be found. My nameplate is not even how I left it. I use LR5 on a Mac. I don't even know where to start to find them all!!
In the menu, check your list of previously used catalogs under the "open recent" menu command.
Sounds like LR opened a new/empty catalog this time.
Retrieving data ...