After a 191 day streak, With no breaks on my part, I have suddenly lost everything! Why? This has happened before.
What do you mean ‘you lost everything?’
You still have the knowledge you gained. All you lost was a number.
I can't explain why you lost your streak, but in the future it might be helpful to buy a streak freeze from the store and keep it in place at all times just in case you accidentally miss a daily deadline. I know I'd be upset if I lost my streak, but psionpete is right: you haven't really lost anything. The knowledge you've gained is what's most important and that can't be taken away.