My mobile model is Sony Xperia L. I have saved some pictures in Gallery Lock. I can see the pictures in folder, but can't open or unhide them. It shows the error message as "File cannot be found and error occurred".
It's possible those files were deleted and the only thing you can see now is the thumbnail of those images. As far as I know, you will have to unlock the files before they can be viewed in the Gallery menu. However, the developers says to uninstall the application, then install it again and go to Settings in Gallery Lock to use the Find/Recover Missing files function. The recovered files will be saved to the following location: /mnt/sdcard/DCIM/recover
Download the app from Google Play: https://play.google.com/store/apps/details?id=com.morrison.gallerylocklite&hl=en