One of my earliest projects as an intern was a small office building, and it wasn't discovered until the end, as the client was moving in that the building didn't have any phone jacks. At no point did I, my employer, the contractor, the electrical subcontractor, the developer, or the client notice this omission!
But phone jacks are a far cry from an elevator in a skyscraper.
The last university project I worked on the first thing the construction office did was check all my drawings for brick ties - it seems on a recent, large project the architect forgot to specify wall ties on the brick veneer (and apparently no one noticed until during construction).
I guess that is why the insurance is called errors and omissions insurance.