As I understand it, the money never left Coinbase. Coinbase identified that transaction as suspicious, blocked it, and alerted the FBI, who would then confirm that it was fraud. The article doesn't say it exactly like that, but that's how I understand it.
True the money was still in coinbase and it was not out of the exchange I guess coinbase detected the transaction as a suspicious transaction and told the details to the FBI so the FBI could detect the fraud or scam, as I see in the article I understood this, there is maybe a good point about the story behind this article whenever an exchange like coinbase put a transaction to on-hold the will check the details of the transaction, to avoid any possible fraudulent.