When Dolphin moves a file to the trash, 2 things are happening: 1. The file itself is moved to ~/.local/share/Trash/files 2. A .trashinfo file is created under ~/.local/share/Trash/info, which hols information about the trashed file If you try to move a file to the trash while no space is left, Dolphin will move the file correctyl to ~/.local/share/Trash/files. As no space is left, the .trashinfo file can't be created however. When you visit the Trash, the files don't apper there, as the .trashinfo file is missing. The only way to delete files at this point (what you should do to free up some space) is knowing in which directory the files were moved and deleting them there.