Well, hopefully nothing that dire - I can't imagine this would happen. Likely though those responsible for the incident will craft an incident report detailing what went wrong and why, as well as how to prevent it in the future - preferably in an automated fashion.
There is no way Google (or I assume any good employer) would fire an employee would for such a mistake. Mistakes happen, they are a part of life in the technical world. You work really hard to make sure the mistakes are minor (which this one is) and fixable, but they are going to happen.
Losing data is really really bad, and if it happens it better be minor and there better be extreme circumstances. If a service goes down, that is bad but shit happens sometimes. Something minor like this is going to make for an entertaining post-mortem, but nothing more. I'm sure Google will do something nice for the person who was affected by it.
Easy rule of thumb for operations: Never make the same mistake twice. You learn from every mistake, but new and amazing ways for things to break are always going to happen.
Source: I worked at Google in operations and made mistakes that were far worse than this
Firing people for making mistakes is a surefire way to ensure that when someone makes a mistake they will do everything they can to cover it up rather than take appropriate action to correct it.
There's also an argument that it makes sure other people will be more careful with their work to try to avoid mistakes. I don't think it's the way to go, but there certainly are managers in the world who do. (Hopefully a vast minority.)
Besides, this is very likely the result of several things all going wrong at once ("a perfect storm"). It's not like there's some dude that's responsible for the "Email" link, who looked at the link and said "yep, that's about right" and saved it to google.
