You made changes to the graphic display of layers in the linked file. After the linked file was reloaded into the Revit project, these changes disappeared.
Issue: To save changes to the graphic display of layers in linked files, select the Preserve Graphic Overrides option on the Manage Links dialog. If this option is not selected, Revit discards graphic overrides when the linked file is reloaded.
Solution: See Control Graphic Overrides for Linked Files.