I often have to make room on my laptop so to do so I move things to an external hard drive. As of late I have noticed that when I put something back on my computer an image that has been take over into another program from Lightroom into Photoshop or another Plug-In, the edited files shows as missing. This is a MAJOR problem because these are usually images that I have worked hours on. Why is this happening to me?
The very simple principle that is used in Lightroom is that the photo must be in the exact location and have the exact same name in your operating system as the name and location in the Lightroom database. If the photo in your operating system is not in that location and doesn't have that name, then Lightroom thinks the image is missing. If you are moving photos to the external drive, then that is most likely the cause of the problem.
So, using the principle above, you can (using your operating system) move the photos back to their original location, or tell Lightroom to change the location of this photo in its database, using these instructions: Adobe Lightroom - Find moved or missing files and folders
In the long run, there's a better way. Put the photos on the external hard drive when they come straight out of the camera. Then, you won't need to move the photos, and you won't need to fix the problem caused by the move, and you won't run out of space on your internal hard drive.