Is there a word for an action that really needs an affordance and doesn’t have one?

This is kind of a conceptual thing I have wondered from time to time. What I am trying to describe is when a user can provide some sort of input to software that will result in some action being taken, but that ability is not obvious and there is no affordance presented to suggest it.

I have just run into a particularly good example of this in Adobe Acrobat XI. I am making a fillable PDF form, and I had opened a properties dialog for one of the (many) fields. I accidentally discovered that if I press the Enter key in this dialog, the result is that it stays up, but now shows properties for the next field in the tab order.

For instance, in the dialog below, pressing the Enter key will not close the dialog, but rather change its "focus" to Text26.

Is there a formal term in UX/HCI theory for this situation? Thanks!