Civil3D Plots erased

[lwratten]

I had a annoying incident today when trying to export to autocad, a drawing containing "plots" that I needed to send to our surveyor.
All the internal plots, ie those made by layout rather than by selecting a polygon, were erased.
The Autocad drawing was not made and all definitions were reset in the Civil3D drawing to the basic large lot configuration.
It is as if I had only started the project.
Unfortunately, the project was saved on exit and has no record of the required subdivision.

Is there previous evidence of this undesirable behavior.
A search of this site does not reveal any like report.

Lindsay