Something else to consider here is that -- if the article I read was correct -- this abduction took place in an area of the West Bank that's supposedly controlled by Israel, not the Palestinian Authority.
Concur, this was an Israeli security zone from what I've read.
These are settlers from what I gather, and they are the most hated by the terror/militant groups. It truly does sound unsafe to be hitchhiking at all, but maybe they trusted the fact the cars passing through had already been checked by Israeli security. Maybe a driver that could pass through a checkpoint with the killers hidden away in the car?