That night the people Richard and Danielle were with were “under the impression” they would be going directly to Danielle’s home over in New Jersey. There is only one reasonable route they would have taken and that was through downtown Philly then across the Ben Franklin Bridge. CCTV on the bridge did not record Richard’s Truck crossing the bridge. It would seem highly improbable that two people could be abducted from a downtown street shortly before midnight without someone noticing something. Not impossible but highly unlikely. The Occam’s Razor explanation is that they decided to go somewhere else instead.
If that is what happened, they couldn’t have been victims of a planned abduction because no one would have known where they were. By a process of elimination, it would seem they experienced a driving mishap and probably ended up in a body of water. Driving after drinking on ice slick roads is an accident waiting to happen. The real problem now is to determine where they might have gone and what bodies of water to search. Was there a Club they liked or an entertainment district young people might go to at the time. An out of town Casino or a favorite diner for a late snack? Maybe just a long drive to have some time to talk alone? Locals would have a better idea where they might have gone; what bodies of water to check. Could Richard have deliberately driven into water as a murder-suicide? Possible but not a conclusion I would jump to.