Stock Market Curiousity

What I don't know about the stock market would fill a library. What I do know was that about six months ago I was very broke and put nearly the family's last $2 grand (the bill money) into Ford stock. I'd only done stocks once before, at the urging of a friend, and lost. But I was reading about Ford having come to an agreement with the UAW union, and how it didn't need bailout money, and out of curiousity looked up the stock price. It was under two bucks a share. So I asked my son Italo if we should bet the bank on it and he said yes. So I did and two weeks later it was at $4 a share and I sold it.
Sometime later I took half the winnings and looked at GM. There was all sorts of good news about GM trucks for sale in China and such and the stock price was at about $0.70 a share. So I bought 1,500. When I did another symbol, not GM, came up. I didn't think anything of it. Heck, the market was easy and I was going to earn another couple of grand real quick.
And the stock did indeed go up. Up to about $1.40 a share, nearly doubling my money. But I figured I'd keep it till it tripled my money.
And then I read an article that said there was no GM stock. That the stock being sold under the name GM (with that new symbol), didn't have any assets. It was just a company formed to sell off the former GM's toxic assets and clean up GM's debt. And when that's done there won't be anything to that new company. Which meant that despite the news services providing all GM information on the stock market pages--about how GM was selling off parts of its European holdings, how truck sales were booming, how well it was doing with the cash for clunkers program and so forth--the stock I held represented nothing. Certainly not GM. So I sold it as fast as I could.
Now I know it's my fault for being a newbie, but I am still wondering how old GM stocks, renamed with a new symbol, can legally be traded. If GM comes out of bankruptcy tomorrow the stocks still will be worthless. Yet they're allowed to be traded on the stock market. Sort of like a legal ponzi scheme, and when one day people holding that stock realize it can never produce a divident, doesn't make anything,and that the company itself will go out of business once all the old GM toxic assets are sold, there will be no more trading of the stock, and whomever has it will lose all their money.
I don't know how that's legal.