The transaction referenced in the indictment clearly happened, but Mueller and his team could have easily searched through the Bitcoin blockchain to find any transaction that paid for a VPN, hosting, or domain registration using Bitcoin on or around the date of the hack.
The indictment makes it sound like the request for 0.026043 BTC came via email. I think that is a bit strange. If you are Russian Military Intelligence about to hack the government of the United States, why would you include references and payment info related to your Bitcoin transactions in hundreds of emails? Surely just keeping track of the Bitcoin addresses on the blockchain would be enough since that is the entire point of the Blockchain. Keeping a reference via email sounds like a good plot for an episode of America’s Dumbest Criminals, not the Russian military.
It is certainly possible that this is exactly what happened, but I think the American people deserve to see some evidence.