The retiring investor says a lot with his actions during times of market froth.Berkshire Hathaway (BRK.B 0.56%) has more cash than the market caps of many large, well-known companies. With an estimated cash pile pushing $400 billion, the conglomerate run by the retiring Warren Buffett is hoarding a safe haven asset in U.S. Treasuries while the rest of the investing world chases the artificial intelligence (AI) trade.What is Buffett trying to tell investors? If we look at his long history as an investor in s ...