Exactly! That's what I heard and read everywhere, that once your gums are gone, they are gone, and never grow back. That's why I was so stunned and amazed when I saw that mine ARE growing back (the only place where it was receded was at one tooth, but it was pretty low, I could see the root which I don't anymore). I am still amazed that it's happening because the accepted truth is that gums don't grow back once gone. I can see the improvements are continuing, I can't believe my eyes sometimes, the change is very apparent. I'll let you know when it's all completely healed :-)
As for the cracks in my mouth, I am wondering if my toothbrush's bristes are too hard, I just got a new one, so it may be how I got the injuries in my mouth. I am trying to be gentler with it and I am going to buy one with softer bristles.
Have you been OPing for your receded gums? Don't worry about what the doctor said, as you can see, things that aren't supposed to happen do!