undetected
adj. 未被发现的；未检测到的
例句
The spy ring had a fifth member as yet still undetected.
特务团伙的第五名成员仍未被发现。
《柯林斯英汉双解大词典》
How could anyone break into the palace undetected?
怎么会有人神不知、鬼不觉地潜入皇宫呢？
《牛津词典》
They managed to get away from the coast undetected.
他们设法了离开海岸，并未被人发现。
