Is it possible that you have saved a PLA file from a project that used that object? Because in that case that version or state of the object can be recovered from the PLA file.

Anne wrote:
I did something real stupid. Saved a nearly empty gdl-description over a gdl-description I had worked with some hours.

I don't know if you've ever contemplated using a Mac, but this would be one reason to do so. It has very clever built-in backup software called Time Machine that automatically makes backups while you work. Better still, it keeps different versions of your work over time, so if the most recent has been mistakenly edited (as in your case) you can step back to the previous one (right back to the point where it was started).

To avoid keeping an overwhelming number of different versions, it keeps the following backup versions:

• - Hourly backups for the past 24 hours;
  - Daily backups for the past month
  - Weekly backups for all previous months

I can still step back to document versions over 2 years old using Time Machine. More info here

Ralph wrote:
...I don't know if you've ever contemplated using a Mac, but this would be one reason to do so. It has very clever built-in backup software called Time Machine that automatically makes backups while you work...

Just to echo Ralph's comment, this OS feature saved me about a 1/2 hour of work yesterday when ArchiCAD locked up. I easily found an earlier version of the file and went on my merry way.

David