Yes, in Oregon, a person can ride a bicycle on a sidewalk even if the street they are riding along has a bicycle lane.
Oregon is a mandatory sidepath law state, which means that the law requires a bicycle operator to use a bicycle lane if one is present instead of riding in the mixed traffic lane. ORS 814.420 Failure to use bicycle lane or path prohibits a person from “operat[ing] a bicycle on any portion of a roadway that is not a bicycle lane or bicycle path when a bicycle lane or bicycle path is adjacent to or near the roadway.”
However, the law only restricts bicycle operators from operating on the roadway when there is a bicycle lane and the sidewalk, while part of the highway, is not part of the roadway. The roadway is “the portion of a highway that is improved, designed or ordinarily used for vehicular travel, exclusive of the shoulder.”