DS9's The Search occurred on stardate 48213..1. Caretaker took place in 48315.8. The first encounter with the Jem'Hadar would have been a while before The Search since it took a while for Sisko to go back to Earth and get the Defiant before we first see it in The Search. That means at least couple months would have passed between the destruction of the Odyssey and Voyager getting lost. More than enough time for Janeway and certain officers to know of them, all that.