I have been using lightroom for a little while now , I no that I don't cataloge my pictures I leave them as the dates that they download. But now I came back from a trip, started downloading my pictures and worked on some and when I went back to work on others lightroom says folder can not be found, it has done this to pictures that I have just downloaded and also to other files from the past and not all, PLEASE HELP. This is Lightroom 5, I have the Lightroom 6 but till my promblem is not solve I'm scared to install it .
Check to make sure you are not using a second catalog by mistake. Take a look at the menu under File/Open-recent.
At the OS level, using Explorer or Finder, check to make sure the image files and folders still exist on your hard drive.
The same thing happened to me. I did a search on all my drives. Cannot find the pictures anywhere.