I've never seen anything like this - I'm running CC 2015 and was operating on a catalogue I made earlier today. I opened it back up this evening, everything worked fine, and I moved the folders that were living inside to another destination on my Mac. The program crashed, and when I went to re-open it, the catalogue was gone. I've looked in the trash, in the application support files, searched my mac for .lrcat files - and it doesn't exist anywhere on my computer anymore. I am completely confounded, has this ever happened to anyone else before?
Please open Lightroom with new or another catalog and then go to Open Recent under the File menu and look for the recent you worked on, also try launching the catalog.
Let us know the outcome.
I have tried opening from Open Recent, but only the older catalogues are shown. I can't find the catalogue anywhere on my computer in either the folders on it or my trash bin - noticed as soon as it happened so haven't moved anything accidentally.
It is a puzzle.
How many catalogs do you have?? Do you have a recent back up??