It's part of the journey. I've lost and gained back, and lost and gained back. It happens. I think it's just part of it for some people. I definitely understand why you feel sad and concerned; it's a lot of hard work to throw away not to mention a threat health wise. But it happens when you aren't quite "there" yet I think. They will hopefully learn from it and next time they lose they will have more tools to keep them from gaining it back.