Investors punished Lockheed Martin stock for anemic sales growth in Q3.By now you've heard the news: Lockheed Martin (LMT -0.13%) reported its third-quarter earnings last week, and the stock is down 11% since that news came out. What you may not know is why Lockheed stock sank so quickly -- and so far.Lockheed Martin is the world's biggest pure-play defense stock, and a giant of the aerospace industry. The problem is that in Q3, it didn't perform particularly well in either aero... or space.Lockheed Martin ...