you could ring the police local to their area on the non emergency line and explain the situation and request that they do a welfare visit and depending on the result, they will take the required action, social services, ambulance, fire , etc.
If a dead body was found then all stops would be pulled out checking internet records etc.
you could, ask for details of their family or a neighbour and ring them to call round.
keep them on line if possible and ask them pertinent questions about how they are feeling.. what happened etc, to pass on to the emergency services if required.
If people did this out of malice, ie pretended to be someone else and asked for help giving a false address, then they may be investigated... especially if this was targetted and was part of a series of harrassment.