"It is not possible to load the scene into memory. The document may be corrupted."

"No es posible cargar la escena en memoria. Es posible que el documento esté dañado."

I simply opened the file after a break and got that message with no layers, no frames and no sound, absolutely nothing. What does this message mean and why did I lose a whole day of work on this file? 

Is there any way to anticipate this happening in the future (other than making regular backups since I was working on this file throughout the morning and didn't have time to make any backups)?