When I press the number 7 on my keyboard, my cube disappears. How do I get it back? Also, how do I go back to default ...

When I press the number 7 on my keyboard, my cube disappears. How do I get it back? Also, how do I go back to default view?
  • aboood319 replied
    me too, i am using 2.78 (version) in blender and the same problem happens to me.(its changing the layer)