It could be a complaint from a member of the public that wasn't reported to you, but ended up in the Minister's office. Or, it could be some sort of personal problem on the part of a staff member that is affecting the work of your unit, unbeknownst to you. Not a great way to enhance a developing career particularly if your boss is also embarrassed. In other practical terms, that which you know nothing about cannot be addressed, and timeliness is important. Why People Don't Tell Before we talk about some specific steps you can apply to encourage people to give you the bad news when you need it, it is good to understand some of the reasons why people hesitate in doing so.
People vary in the degree to which they are comfortable communicating bad news.
Some people, for example, have difficulty tolerating conflict and associate bad news with conflict situations. Unfortunately, there isn't much you can do to counter-act these individual differences directly. The second source of hesitancy is your own behaviour. Obviously you wouldn't deliberately set up such a scenario, but your personal style may be sufficiently emotional to scare off at least some people. Managers that are perceived as problem-solvers are less likely to intimidate staff into silence.