Sheldon Whitehouse was the Dem who wasn't there for the vote. He's a great guy, and very responsible, so I don't get what happened. The vote was 49-49. Presumably both Mitch and the missing Dem, Sheldon Whitehouse, would have voted to disallow the tariffs.
But in any case, there was never any hope that it would have passed in the House, which would have been necessary.