have (one's) head in the sand

To refuse to acknowledge or deal with problems, danger, or difficulty, especially in the hopes that they will resolve themselves. The phrase is a reference to ostriches, which were believed (incorrectly) to hide their heads in the ground at the sight of approaching danger. Your department clearly has its head in the sand regarding this security breach! You can't just always have your head in the sand whenever you're confronted with a problem in your relationship.