Question regarding Va. mediation?

If there is a written agreement in place, signed by both parties and attorney and an amendment needs to be made, is the original agreement completly null & void? All that was wanted was a few adjustments made a couple lines changed, that's it. The mediator than wrote a completly different agreement and left out many key points from the original. When I asked why wasn't she just ading in the new details, she told me consider the original agreement done and it has no legal enforcement. Am I confused on what the meaning of amending it was? This is in Virginia btw. If you can offer any advice or link to reputable site where I can view my rights, I would greatly appreciate it.