Using RECOVER command you can recover as much data as possible from AutoCAD files with DWG, DWT and DWS extension. This command can be used for files which are damaged to such an extent that it cant even be opened by AutoCAD.
Open a blank drawing and type RECOVER on command line press enter it will open file browser select drawing which is damaged and click open. AutoCAD will attempt to recover as much data as possible from that drawing and it will open recovered drawing in a new tab of same AutoCAD window.
Moreover, in case it isn't help to restore dwg. I usually use Google, I found following for your case