Seems simple, let the cops pretend to be customers, do an offer, see if it was a hoax or not, done.
Of course the police departments don't have the brainpower to think up such a simple check so it's waiting for some official who has a wayward son or daughter who comes up with the idea and it then moving down the pipeline to the police manual and then it can be used.

The parents were (and are?) drug addicts according to the Canadian national news provided by cops. They provided a phone number that was real to the couple. Doesn't seem like a hoax to me. That's why the baby was taken - at the very least, a terrible sense of judgement for this 2.