When Sisko & Jennifer are about to be cut off by three Cardassians, Sisko fires his weapon. The first Cardassian starts falling backwards before Sisko's shot reaches him.
Sisko refers to alternate-universe Jadzia as "Dax" but the best logic holds that alternate-universe Jadzia was not joined. It was most likely a pretty careless mistake by the writers, starting to treat "Dax" like just her last name rather than an indication of joined status.