It's true that one Calder's nice scarves would probably have done a better job of looking after a teenager she is using as an informant about some dangerous local drug dealers.
I can't remember from that first episode when he's with Rosh and Calder in the car when they raid that trawler -- what did the police have on him that made them able to use him for information? Whatever it was, it seems incredibly irresponsible of them to bring their informant with them to the raid!
Even the world's dopiest drug dealer is probably going to conclude that the local teenage ne'er do well who is actually sitting in the back of the car with two detectives is the grass!
And, even given that no drugs were found on the boat, it seems pretty obvious that someone would have been keeping an eye on the trawler, and would have seen Louden in the car and then running.
Which makes it incredibly stupid to then pressure the same kid into trying to find out more about the identity of the kingpin. You might as well have sent him into the fish factory with a hoodie that said COPPERS' NARK on the front.