Bitcoin owners are getting rich because the cryptocurrency has soared. But what happens when you can’t access that wealth because you forgot the password to your digital wallet? Stefan Thomas, a German-born programmer living in San Francisco, has two guesses left to figure out a password that is worth, as of this week, about $220 million. The password will let him unlock a small hard drive, known as an IronKey, which contains the private keys to a digital wallet that holds 7,002 Bitcoin. While the price of Bitcoin dropped sharply on Monday, it is still up more than 50 percent...