And there's something called the "good-faith exception" for unreasonable warrants: If you get a warrant where it's required (or in this case, where the government tried to argue it wasn't!), and a magistrate grants that warrant, it's a legal warrant so long as all participants were acting in good faith, believing their actions to be legal. Even if a court later finds that the warrant should not have been issued for one reason or another.

This is why Alito was grouchy during oral arguments and in his opinion that the Court took the case in the first place. The police got a warrant, acting in good faith. It allowed them to identify the criminal, who was later convicted. It wasn't clear that any decision by the court on the warrant requirement would have anything but an advisory effect, and SCOTUS doesn't do advisory opinions by longstanding tradition.