What a ridiculous thing to assume. Especially since TFA features a statement literally saying "a warrant was obtained for the surveillance equipment."
I'm happy to concede that policing in America has long eroded that trust but it's still a requirement that you obey and openly communicate with anyone identifying themselves as law enforcement.
There is no requirement that you communicate openly with police. See: the Fifth Amendment to the US Constitution.
I'd understand the argument for why they're incentivized to get a warrant in the first place (even assuming parallel construction is a viable alternative to getting a warrant as they may be caught) but that doesn't mean they wouldn't lie after they got caught screwing up.