看一篇講述牛奶營養(yǎng)方面文章有一句話：

In fact, in 1985，the United StatesDepartment of Agriculture officially recommended a switch to skim milk, threeglasses of it a day. But, more recently, we've begun collecting evidence thatsays the 美元A might be missing an important piece of story.

請教大伙，這句話中進行時態(tài)be missing里的動詞miss完全是一個過去的動作，語義也無需強調(diào)正在進行，為什么用進行時態(tài)呢？

并請與一些其他例句來講明如此的表達辦法?

《韋氏高階》動詞miss解釋之一及例句如下，你的句子中miss就是這種使用方法。

3 [+ object] : to be without : to lack — used in the phrase be missing

He was missing one of his front teeth. [=he did not have one of his front teeth; one of his front teeth was missing]

The old house is missing some of its windows.