In design, white space is the part of a page or illustration that is left unmarked. There are no images, words, or even small flourishes. It is completely blank, left as the silence among the other design elements on the page.
That silence is important. It lets the viewer's mind breathe. It gives them a place to rest their eyes as they think about everything else on the page. That silence gives the viewer the space to think.
Silence in conversation is equally as powerful. It is a pause between thoughts. It allows the speakers to think about the words that have been said and the words that should come next.
However, complete silence on one side of a conversation takes on a different meaning. It is no longer contemplative. It is more than a pause. It is a confession. What it is a confession of is unclear, because no one is mind reader. But, especially when a question goes unanswered, that silence can speak louder than one ever intended.
That silence can mean someone does not know the answer. Or they feel threatened. Or they are angry you even dared to ask the question. Or they do not have enough respect to offer an answer.
Silence like this is unhelpful. Even an emoji shrug would be more useful.
All relationships are bi-directional, whether they be personal or professional, between two peers or two people of differing ranks. The choice to remain silent in any case speaks volumes, and intent is irrelevant. It speaks to a person's character and to their views of the relationship. It loses respect, friendship, and trust – and those things are not easily replaced.