It seems you have renamed them with an Invalid folder name and or you have moved and renamed them to the ROOT of the Macintosh HD which the newer versions of OS X doesn't like and does really give the user, the Username, access to. That is unless you, your Username, as an Administrator changes the permissions on the ROOT of the Macintosh HD.
It is an OS problem and or restriction. Either change the permissions on the ROOT of the Macintosh HD or Create a folder under your Username to store your images.
Thanks for your suggestions! ^^
Ok I'm pretty sure the folder is under my username. It's within my "pictures" folder.
How do I change ROOT permissions?
That is not what your screen shot is showing. It shows Macintosh HD then directly under that you have a bunch of folders. That can happen if you don't have Show Parent folder selected. With the show parent turned off you never really know the true Path to your files and folders. I guess that is a Mac thing.
Hi I was able to confirm that the folder was in my username, but I was able to fix the problem. I enabled root permissions and dragged the folder to another location so that I could "find" it again in LR. This worked and I didn't lose any of my work.
Thanks so much for your help!
By default, LR does not show the folder tree like Finder does. To fix that, right-click on a folder and select "show parent". Repeat as needed.