When something isn't directly our fault, it's a natural reaction to shift the blame. He was supposed to... They didn't follow procedure... So-and-so said they had it...
These statements may be totally valid; it wasn't your fault. But if you could have done something to fill the gap, make sure it was done, push it to completion; you also have the option of owning the mistake. It seems foolish to fall on a sword when it really wasn't your responsibility, but doing so reveals character.
Maybe owning the problem is to protect your team. Perhaps it's showing loyalty to leadership. Whatever the case may be, owning it yourself as oppose to passing the buck is a higher call.