First, let me explain how you can loose it. Hold the command line from top of it and extract it and bring it to the middle of the drawing. Then close the window by clicking the X symbol on the upper right corner of it. Before you close the window, AutoCAD will prompt the alert message that you can see below.
Fig.1 The last window you can see before losting your command line...
It is obviously giving the message of “Hey buddy, don’t close it, if you close it, then it will be very hard to find it again! However, even if you close it you can press CTRL+9 and bring it back.
” If you don’t read the message and still close it, then you can press CTRL+9 to bring it back.
Sometimes, command line is not lost, but it may be stuck right under the window. The solution of this problem is easier. If you can hold it by using the mouse, then you can move it upwards. But, if you are unable to grab it, then you can press any visible location inside the command line and select “Move”.
I hope you will not loose it again.