I guess the Olympia could have been out of contact with the Federation; Cusak did mention that they were on a long range exploration mission.
Ya.. I thought about that. I guess what triggered my thoughts was that she mentioned that they had been gone 8 years. One quick search in their records would show that it would have been a little longer, like 11 or 12 years.
Upon reflection I think my concern would have made for a decent plot line. Someone (Sisko) would have had to tell her the truth, that they were speaking to her from the future and rescue would be impossible. This is almost similar (almost) to "the Children of Time" where Kira learns that she is/was dead already (or going to be