I konw there have been several threads on missing participants, and I've read most of them. However, in this case, the participant is dead, not missing. The beneficiary per the plan document is the estate, but there evidently is no estate, or no one to handle the estate. And there seems to be no living family - even distant family. Based on this set of facts, should the plan do anything different than what has been suggested in the missing participant threads?

Every decedent has an estate. If there are no living relatives then usually an administrator will be appointed to find the next of kin. Your job is to find out who will administer the decedent's estate. Usually it s a person appointed by the local judge or surrogate.