Black bears aren't interested in cats, but most cats are afraid of bears. Sadie more than likely knew the bear was in the yard, and went into hiding. The semi-feral boy who lives in my yard didn't show up for almost half the day the last time a bear came through.
Is Sadie an indoor-outdoor cat? Please look at this website, www.catsinthebag.org if she doesn't come home soon. Chances are, though, if she's used to going outside, that she hasn't shown up because the bear gave her a good scare. Hope she'll soon come home.