I'm sure you'll get plenty of answers from the professionals here, but even as low-time heli pilot I know it's not unrecoverable - though when it happens IRL it may be a bit of a shock, like any emergency.
You can enter autorotation, supposing of course you have somewhere to go. Or in the R44 (yes, I know), and I guess most other types, you can fly in a peculiar feeling slip at about 70 knots until you can find somewhere safe to autorotate to.
This is when your instructor has spent half an hour prepping you for the exercise, then counts down before putting the pedals in a more-or-less neutral position. How it works when the TR suddenly parts company with the airframe, or the drive snaps, is another matter. By the time you've realised what's happening, instinctively tried to counter it with pedal, realised it's getting worse, had the "aha! TR failure" light bulb go on, and dropped the collective... you'll be going round quite fast, so your reactions may not be quite that good.