Well my durango happens to have key holes on both front and the rear door. I too have opened the passenger door countless times with my key while all the others are locked. I dont have a remote or any sort of oem key fob either. Im thinking it might have been the case where all the other doors were locked minus the front passenger door. Thus leading to it going off thinking i was breaking ino it. But even that doesnt make sense seeing as how my doors auto lock after i drive the truck.