I just updated my Lightroom 5.3 to 5.6. I have 9 years of travel folders under one catalog, about 30,000 images. Two of my folders, years 2012 and 2014, appeared after the update with all files. Five folders appeared in Lightroom library showing " 0 " images. Two folders in the library state that I have less than half of the images that I originally had in the folder. In all the years of my updating Lightroom, this has never happened. I would appreciate some help...... Thanks, Travelenfree
Never happened to me, either.
Can you be certain that the missing folders and files were there immediately before the upgrade?
Are the folders missing from your hard drive, as well as from Lightroom? If so, it's almost certainly not a Lightroom problem, as Lightroom doesn't delete folders unless you ask it too - I think a bug that did that isn't likely.
If the files and folders are present on the hard drive, have you tried your latest Lightroom catalog backup? Unless you've altered the settings, it does one each week. If you go back to a previous catalog, you should be able to recover any recent work by a bit of "import from catalog" to import recent work from the latest catalog.
If the files and folders are gone from your drive, I assume you've got a backup. However, I think I'd want to find out how the files got lost because, as I say, I doubt Lightroom did it.