(Aloha, OR)  --  Police are searching for a missing 15-year-old girl who they believe might be with her alleged sexual abuser.  Investigators say Annieka Vaughan ran away from her Aloha home Monday.  Police say 23-year-old Zachary Petersen of Pasco, Washington disappeared the same day.  Petersen is being investigated by Benton County sheriff's deputies for the alleged sexual abuse of Vaughan in late September.  Anyone with information on their whereabouts is urged to contact police.