The way I know is to click on "Zoom to extents", which icon is a sheet with arrows each side or press Ctrl-Backspace.
The other alternative is to look out to any layer turned off (remember never to turn Layer 0 off). Turn them all on and press Ctrl-A (select all) and chose in the menu View / Selection info in the Palettes section.
Any object available will appear in that section.
I truly hope you will have success with that.