They're making headlines.
In one of my earliest posts I wrote about my version of the headline prediction. In my version your prediction is only half-accurate and the implication is that you did something to make the other half of your prediction (some awful event) not occur. This is, of course, exactly what you would do if you had the ability to predict future headlines and you were at all a decent human being.
My suggestion of what you should do if some truly horrendous thing happened (a huge terror attack or something) was this:
If that happened I wouldn't switch the prediction at all. I'd let her open the envelope and reveal the actual prediction I wrote and sealed in the envelope which says:
Pony rescues puppy from river.
Then I would look at her and say, "Fuck. I'm terrible at this."
A couple people wrote me at the time to say that approach doesn't really solve the problem. But I think it precisely solves the problem. No, it might not solve the problem of how it appears in your fake world of magical powers. But it solves the problem of how to approach the issue in the real world that you're inhabiting with your spectator.
It's such a magician/mentalist thing to think, "What if a dirty bomb kills 40,000 people in downtown Seattle... how is this going to affect me." I think you'll manage. I don't think your target audience is going to mind. They're not going to be like, "What a day! First my aunt and uncle get crushed under the Space Needle. And now it turns out Pete can't really predict the future!"
I'm mentioning this now for two reasons. The first is because I have some posts coming up about failure and screwing up tricks. The second is because I've come across another perfect headline to start with in your prediction envelope in case you can't switch it out.