can't open drawing

We were working on a drawing and closed out like we normally would (I think)
and now when we try and open the drawing, it tell us that the drawing file
is not valid. It shows up in the preview screen, but will not open. We are
using the latest acad and survcadd. Any help would be appreciated? Also
the .bak file got deleted somehow. Is there a way to get the file the way
it was last friday? Hope you guys can help.
and now when we try and open the drawing, it tell us that the drawing file
is not valid. It shows up in the preview screen, but will not open. We are
using the latest acad and survcadd. Any help would be appreciated? Also
the .bak file got deleted somehow. Is there a way to get the file the way
it was last friday? Hope you guys can help.