When you make changes to your BSV and you either put the BS under Full Test (Ctrl T) or try and close the configurator, Aware will show you a dialog advising...
Business Space xxxxxx version x.x has changed
Update the Business Space Version?
YOU SHOULD ALWAYS answer Yes.
If you answer No and the Configuration is closed then all the work you have done since the last save is gone.
I make a habit the use Full Test (Ctrl T) rather than Quick Test (Ctrl Q) every so often and especially after any structural changes.
The only way you would have lost your work is if either...
a. You answered No when you were asked that question
or
b. a crash.... which it does not sound like the case.
Test this for yourself.....and it will give you confidence that Aware is sound and teach you good habits.
Make some small changes and try and close the Configurator.... Answer No to the dialog..... when you come back the changes will be gone.
Now do the same thing and answer Yes... Changes will still be there when you come back....
And of course.... RULE Number 1.
ALWAYS, ALWAYS, ALWAYS put the BS under Full Test and export the BSV at the end of every session BEFORE closing the Configurator.