you can only show in an MEP the parts that are visible in 3D in the display state you are using.
If you want them to appear on your Layout, you have to create a display state (or a configuration, depending on how you work) where these parts appear.
Your drawing reflects your active 3D (just in case you have several configurations), so if the room is hidden there then it will be hidden in your MEP, so as Luca Prieur says, the best is to make a configuration with this unhidden one and there your part in your MEP will be displayed
You can load an assembly with its active components fully resolved or lightened. Both parts and sub-assemblies can be lightened.
When a component is fully resolved, all the data in the model is loaded into memory.
When a component is lightened, only a portion of the model data is loaded into memory. The remaining data is loaded when you need it.
You can significantly improve the performance of large assemblies by using lightweight components. It is faster to load an assembly with lightweight components than to load it with fully resolved components. Assemblies with lighter components are rebuilt faster because there is less data to evaluate.
Lean components are effective because the model data is loaded as and when you need it. Only the components that are affected by the changes made during the editing session are fully resolved. You can perform the following assembly operations on lightweight components without solving them:
Add/Remove Constraints
Selection of edges/faces/components
Assembly functions
Measure
Section properties
Mass properties
Exploded views
Motion Simulation
Interference detection
Collision detection
Annotations
Odds
Assembly Reference Geometry
Cross-sectional views
Advanced component selection
When a component is lightened, a feather appears on the component 's icon in the FeatureManager authoring tree.
By right-clicking on the view in question and clicking on "tangent edges visible" the view comes back (it never left elsewhere). I often have this souçis myself! Try it may solve your problem!