It's definitely easier for a reporter to be a little over eager with a story and run it before being fully vetted than it is to co-opt federal agencies and independent auditors.
I'm not saying that it's not possible for the situation you described to have happened, just that it would be an extreme outlier.
Given the nature of their doubling down upfront about it, it could be quite problematic for them to admit they were Very Wrong.
It's also possibly permanently going to be unclear whether this is factually accurate unless someone discovers a compromised system or the sources for the reporters provide enough information on why they believe what they do to actually investigate.
If they were to publicly say they were wrong then suddenly that would be News the way the original reporting was. If they don't then only specialty publications will cover the failure to pan out.
Bloomberg rewards their "journalists" for moving markets and use the promise of market leading scoops as the carrot to win subscriptions. An admission of generating fake news hurts their core business deeply.
I'm not saying that it's not possible for the situation you described to have happened, just that it would be an extreme outlier.