Gone as in "no longer in my catalog" or gone as in "no longer on my hard drive"?
I don't recall if the default action of the LR6 install is to create a new catalog or migrate the existing one.
Go to menu:/File/Open recent/
and see if you need to open a previous catalog.
When you open a LR5 catalog with LR6, you will be prompted to migrate the old data to a new LR6-format catalog (no changes to the LR5 catalog).
YOU!! Are my favorite friend! Thank you! That worked and I am probably going to stay up all nigh editing them so I no longer have to worry! Thank you so so so very much!!
So I can see the photos but it says file cannot be found? Anything I can do?
First go to the Library, grid view. Right-click on the "missing" image and select "go to folder in library". Check the markings on the folder in the Folders panel to see if the folder is "missing". It might have been moved/renamed on your hard drive.
If the folder is not missing, right-click on the missing image and select "show in Explorer/Finder". Verify that the image is actually on your hard drive where LR thinks it should be (moved/renamed/deleted).