There are arguments that might effectively be deployed in Lisa Raitt's defence.
The government could argue, for instance, that the documents left behind at CTV's studios weren't really all that sensitive (which might indeed be the case if they were estimates, as seems to be the case). It could also be up front and acknowledge that Raitt - unlike Maxime Bernier - has shown no pattern of poor judgment, and needn't lose her job for one mistake.
What the government is arguing, though - that Raitt is not to blame, because it was all her staffer's fault - is pretty weak.
The buck stops with ministers. The good news is that they get to take credit for their anonymous staff's hard work. The bad news is that they also have to answer for that anonymous staff's mistakes.
Personally, I'm more concerned about figuring out if there's any systemic problem or shortcoming with the tracking of documents. But If leaving that binder behind - and not noticing its absence for a week - is a firing offence for the staffer, it should be a firing offence for the minister.