"He was lost" describes the person's state of being lost, while "he got lost" describes the process of becoming lost.

to be lost = the situation when you don't know where you are - I turned left on the street and then I realized I was lost. to get lost = to lose one's way - I wanted to visit my friend, but I got lost on the way to his house.

He was lost: the others can not find him He got lost: he can not find the way