But the transactions were final, just as it would be if your employee stole the day's cash and escaped somewhere you couldn't find them. Reversible would mean you could press a few buttons on the cash register and poof, the money's back in it and not the pocket of the thief.

Tracking down said thief and taking the bag of money back in this metaphor constitutes a new transaction. As is subpoenaing Dropbox and gaining access to the poorly encrypted list of private keys from these Bitfinex rapper/hackers.