I have that problem, and unfortunally the code disappears REALLY from .VCX/.VCT.
What have happened I think that is a VFP bug.
But you can avoid this to happen again.
When some VFP program run and use a classlibrary (a .vcx) the .vcx definition remains on memory, and when you open it on class designer, the methods code
come blank, because the vcx is in use. Until this step, the code is already on .VCX / .VCT
But, if in this condition you modify anything on that class and save it, so just what you have modified is saved. The old code is lost, really lost.

So, if you open a .VCX on class designer and the methods come with "default" (no code), close it and run the following on command window:

CLEAR ALL
CLOSE ALL
RELEASE ALL

Open your .vcx again and you will see that your code is recovered IF (repeat IF) you don't saved your .vcx when the methods code come in blank.

I hope this helps.