I was modelling and then I pressed some key sequence that made Blender hide every single layer and object in my scene! But everything is hidden only in the ‘Default’ workspace, the others show my work. Even the small layer panel in the bottom of the 3D view disappeared.
I would like to know what happened, and more important: what can I do to make everything appear again in this workspace.
You have an object (Cylinder.003) in Local View mode… although it’s apparently hidden or no mesh in that object. Local mode displays selected objects alone and centered. In the 3Dview View menu > View Global/Local. Shortcut is Numpad / (forward slash) key.
You can see the current view mode (Local) at top left of 3Dview in your first pic.