I have stumbled across two methods to bring up the command line (neither of which I saw on this thread). I don't know what version you're running, but I'm running 2010. The command line was missing, but I could still type commands, which would often appear on the screen as if I were typing text into the drawing, and then hit enter or space to execute.
On a whim, I typed "commandline" and it appeared. I then closed the command line and in the process was shown a second method of hiding or showing the command line: Control + 9.
I hope one of these works for you.