GarnerForEmmy
Cadet
I think Sydney was smart enough to realize that since Sark was after the same thing she was, he must know something, possibly about her missing years, but at the very least he must have some information that at some point could be helpful to her. Now granted, it might be hard for her to get that info out of him but it would be extremely diffecult for her to get it out of him if he were dead.