That is not even close to being true. Masturbation does not harm males or females (assuming they don't masturbate with sharp objects or anything like that
xp ). In fact, masturbation may have health benefits.
I am only aware of one case where someone was said to have a "stone baby." This was not a fake pregnancy, however. It was said to be a baby that died before it was born and calcified, basically turning hard, like stone.
http://www.obgyn.net/medical.asp?page=/ENGLISH/PUBS/ARTICLES/Stone_Baby This woman's baby died inside of her, and she left its dead body in hers for three years according to this article. That's pretty weird. Typically, when your baby is that big and dies, you go to the hospital, not just sit on your butt. So if this story is true, the woman sounds like a real weirdo to me anyway.
Like I said, that is the only time I have ever heard that term used, and that does not sound like what you described. What you described would be called a false pregnancy. I very rarely hear about humans having a false pregnancy. I sometimes hear about animals having them, however. Sometimes animals will have a baby that dies. The mother may then show signs of another pregnancy, even though she is not pregnant. It usually happens in dogs, cats, and rabbits.
So, like I said, whoever told you that really does not know their stuff, and you probably shouldn't take any sex or pregnancy advice from them because that wasn't just a little incorrect; it was way the heck out there.
xp Women can't get pregnant from masturbation. If a woman had sex and wanted to know if she was pregnant, she could just go to the doctor and ask or even go to the drug store and get a simple pregnancy test. It's not a big deal.