Obviously it could have been found during planning but it never would have. It's hard to get people to think in that much detail without anything concrete.
Edit: with the exception of literal rocket scientists -- they're very good at planning and getting the details right compared to the average person.
Edit: Do you really want to be an evangelist for mediocrity? You should give thinking things through a try; none of us get it right even close to all the time, but I think you will be surprised by how effective you are at it.
Sometimes you have to do the work and build something that isn't fully specified. Or when management says they want a Facebook clone and then walks away, you have to be willing to say "no, you have to come back the table on that one".
I think the pendulum has swung too far the other way, however, and it is not hard to find opinions (and Stack Overflow comments and sometimes answers) stating, in effect, that the only valid way to develop code is to write some and try it. For the most part, I think these authors have not considered of how much thinking ahead goes into making even that work, and if they did, they would not be so dogmatic about deprecating it.
Three areas, of definite relevance to ordinary commercial applications, where I think thinking ahead is more or less essential to success, are security, concurrency and performance.
Instead the article is about programmers who code without the involvement of stakeholders at all. The inclusion of agile is a bit of red herring.
