If the plan's administrator has not decided that the participant is dead and no one has submitted a claim for a death benefit, the administrator might consider that it has no current need to discern who might be a beneficiary.
Consider that reaching-out efforts often spark false claims.
If the participant's employment ended in 2014 (and the balance is low enough to call for an involuntary distribution), shouldn't a routine processing of involuntary distributions have emptied the account before 2016?
The plan's administrator should use or engage identity-control, death-information, and address-information services that are under the administrator's control, without communication to a person who seems to be the participant's relative.