Mercedes, Toyota and Panasonic all bought Tesla stock back when Tesla's entire lineup was one sports car. If they'd just held on, those shares would be worth about $52 billion today, which is more than Mercedes-Benz is worth as a whole company. All three sold. And if you'd been running any of them, you probably would have sold too. Mercedes (Daimler, back then) went first. In the 60 Minutes clip Elon says the $50 million check Daimler wrote in May 2009 is what actually saved Tesla, and that…