conspicuous by one's absence是英语习语，现在已经用的不多了，很多人认为是陈词滥调，一般多见正式文体。这里用in和from 都是正确的。请看英美报刊例句：

1. Hope is conspicuous by its absence in the nomenclature of those Danish districts.
2.Australia conspicuous by its absence in climate debate (新闻报道题目）
3.New Zealand is conspicuous by its absence from the Economist’s Safe Cities Index.
4.The small and generally well-integrated population of Maghrebis there was conspicuous by its absence from the demonstration.

(1)one's absence in +名词 表示“暂离某地或者暂时不存在/出现”

He played no part in the game and was conspicuous by his absence in the post-match celebrations.  

比赛时他没有上场，并且由于没有参加赛后的庆祝活动而引起了大家的关注。

Her presence in nature was felt in spring, her absence in winter.  

她在春天里到来, 在冬季中离去.

Of course, pure market systems are notable for their absence in the real world. 

当然, 在现实世界中,纯粹市场体系显然是不存在的.

The process we use to encourage attendance and manage absence in Tesco.  

在Tesco用于鼓励出勤并管理缺勤率的流程.

A glaring absence in the story of China in Africa is Chinese manufacturing.  

中国在非洲的故事有一个明显缺失——中国制造业.

He cleared up the question of his absence in the presence of all his classmates. 他当着全班同学的面澄清了他缺席的疑团.

(2)one's absence from +名词 表示不参加/缺席/缺课

The teacher demanded an explanation for his absence from class.  

老师要他对缺课作出解释.

He was desperately eager to be back after more than a week's absence from school.  

他一个多星期没有到学校,回校之心甚切.

Perhaps Nim's absence from the screen today would lower Leah's status among her friends. 

也许尼姆今天没在荧光屏上出现会降低莉娅在她朋友中的威信.

You might be wondering about the absence from our list of the Born postulate.  

你们可能感到惊讶,在我们的列举中没有玻恩的假设.

I wrote an excuse for my absence from school.  

我写了一张请假条,说明缺课的原因.

The little boy manufactured a tale for his absence from school.  

小男孩为自己缺课编造了一个故事.