All materials are packed. Backups of materials can be found within assets. Use File>Append to append all the contents (or whichever specific content you wish) into your scene. Most modifiers are ON, so before appending, you might want to knock a few of the modifiers off so it doesn't bog down your scene or lead to crash. Objects that contain a "red hot" material, go into edit mode and select all (A-Key) and then in the materials list, in the upper right select the red hot shader and click "assign."