He was looking for his lost keys.他在寻找丢失的钥匙。

lost baggage/luggage丢失的行李

Many have tried to find the ruins of the lost city.许多人都力图找到那座湮灭之城的遗迹。

The child was lost.那孩子迷路了。

We took a wrong turn and got lost.我们拐错了弯，迷路了。

a lost puppy迷路的小狗

Hold my hand. I don't want you to get lost.抓住我的手。我不想让你迷路。

He has been trying to recapture his lost youth.他一直在努力追回逝去的青春。

She's been lagging at the polls, but hopes to recover/recoup lost ground with tonight's debate. [=she hopes to gain again support she had lost]她在民意调查中一直落后，但她希望通过今晚的辩论收复失地。

a lost civilization失落的文明

It's a lost art.这是一门失传的艺术。

The original music is lost to us forever.原版音乐永远地失传了。

a lost opportunity/chance [=an opportunity that was not used]错过的机会

The strike has cost the company millions in lost sales/earnings/revenue. [=sales/earnings/revenue that the company would have had if the strike had not happened]罢工使公司损失了几百万美元的销售额/收入/收益。

We need to work faster to make up for lost time. [=we need to work faster because we did not get enough of the work done before now]我们需要加快工作来弥补失去的时间。

a lost battle败仗

The game was irretrievably/hopelessly lost by the end of the first half.比赛在上半场结束时就已经输定了。

Finishing the project on time seemed like a lost cause. [=finishing the project on time seemed impossible]按时完工似乎没有一点希望。

When she first moved to the city she felt a bit lost and out of her depth.她刚搬进城里时有点不知所措，力不从心。

I don't know how I ever managed without my computer: I'd be totally lost without it!我不知道没有电脑我该怎么办——肯定会一筹莫展！

I depend on her for everything. I'd be lost without her.我什么事都靠她。没有她我会不知所措。

a lost soul [=a lonely and unhappy person]失魂落魄的人

When he's reading a book he's lost to the world.他看书的时候全神贯注。

He was lost in his book.他沉浸于书中。

She was lost in thought. [=she was thinking about something and not noticing the people and things around her]她陷入沉思。

He seems to be lost in a world of his own.他似乎沉浸在自己的世界中。

lost in (a) reverie陷入幻想