"Hidden" Mesh

Ok, new member here(not new user), I’ve got a bit of a problem.

I have hidden several meshes and a light and a camera. However blender doesn’t seem to be able to unhide them.

Can anyone help me figure out exactly what is going on here.

Alto mare dunno.blend (972 KB)Alto mare dunno.blend (972 KB)

Look in the top left corner of the 3d viewport. It is telling you useful information. It is telling you that you are in Local view mode.
Toggle between Local and Global view with Numpad / or from the View menu
See https://www.blender.org/manual/getting_started/basics/navigating/3d_view.html?highlight=local#local-and-global-view

Thank you so much.