It is possible that LE knows she drove to dock, knows she met OM there...but cannot prove anything beyond that. Her father seems determined that she came to harm at the hands of someone known to her. His pleas tend to be asking for someone who knows where she ended up to come forward, more directed toward a witness/accomplice than the perp, IMO.
Not sure if I agree that more than one person knows where she is, or if so, that the accomplice/witness would be compelled to talk in any case. Usually it takes divorces, deaths or other life changes for this to happen, which can be years away. JMO
Appealing to conscious does not seem to be working.