① under sb's nose就在某人眼皮底下 in sb's presence, usually without him noticing anything。
这个英语习语表达一般是指“目空一切，胆大包天的态度”，但是它也可以用来表示“离人们很近，本应注意到却未能发现的事物或人”。
②扩展(from) under your nose在…眼皮子底下发生（指坏事就在眼前发生但却没被意识到或无法被阻止） used about something bad that happens in an obvious way but in a way that you do not notice or cannot prevent。

【例句】
The book I was looking for was right under my nose.
我要找的书就在我面前。

She stole the shoes from under the assi
她在售货员的眼皮子底下把鞋偷走了。