This is the 4579th most frequent Catalan word.
perduts
"Perduts" means "lost" in English.
Here, 'perduts' is used as an adjective describing the state of the hikers being unable to find their way.
Els excursionistes estaven perduts a la muntanya.
The hikers were lost in the mountain.
In this sentence, 'perduts' conveys the idea of something being wasted, referring to the efforts.
Els nostres esforços per ajudar-los han estat perduts.
Our efforts to help them have been wasted.
Here, 'perduts' again acts as an adjective, describing the books as missing or misplaced.