"I find it very hard to believe. People generally are not that stupid. Sonar operators (if that is how they were listening) would have in depth technical knowledge of their equipment."
YRP, They may have knowledge of their equipment, but not knowledge of what frequency to listen for from an aircrafts acoustic beacon. That's not something they do everyday.
And yes, people are generally that stupid. They just front like they know what's going on. It's a natural defense mechanism.
As far as a reference, look it up yourself. You'll remember it longer. Believe me, if you do your own research, you'll find how competent/incompetent people, governments, businesses, etc really are!