autocad file has invisible content

[elifish]

Bye to all,
I have not found, at least I believe it causes my beginner experience in the forums, some posts that referred to how much I am trying to understand.
I worked all morning seamlessly at a 3d file with autocad 2007, suddenly as I made a king(gen) to update it, I no longer saw any line. of course I also tried to restart the file, and the problem turned out equal.
Can someone help me, considering that it is very important material?
Thank you.
elifish

 

[Albertuan]

it happened to me several times but saving everything, restarting the pc and opening again the file always returned to me.

if not succeeds try to open it with file -> drawing utility -> recovers.