But now it’s going to be the ultimate “missing heir” story - the zombie missing heir!
I suspect we’ve had a thread already about whether zombies can inherit…
Ah, but why would a ghost be looking for info on zombies? makes one furiously to think…
Just to add another mystery with missing/estranged heirs: Brat Farrer, by Josephine Tey, set in England. Twin boys, one few minutes older than the other (obviously). The older boy is at the seaside one day and goes off a cliff. His torn clothes and a pen knife (I think) are found at the rocks at the bottom of the cliff. Body never found. Younger brother is now the heir presumptive to the estate.
Many years later, just as the younger twin is about to reach his majority and gain possession of the inheritence, a dissolute friend (really just a skeevy hanger-on) of the family spots someone looking exactly like the now-twentysomething younger twin. This lookalike–the eponymous Brat Farrer–claims he knows nothing about this family and in fact has spent most of his time in America. The skeezy friend convinces him to imitate the older twin, show up and inherit everything right out from under the younger twin’s nose. Shan’t tell you how it all ends.
I’m pretty sure Agatha Christie must’ve done this plot about five times in her catalogue. Rex Stout has at least two versions of this, first in (I think) “A Window for Death,” where an estranged brother who was accused of his father’s murder by opening a window and causing the father to die via pneumonia (it makes more sense in the book, honest) suddenly shows up looking for his inheritence.
Another one is in Prisoner’s Base (one of his best, which is high praise indeed), where the twist to the tale involves a young woman, about to come into her inheritance. She’s had a bit of a wild streak at an earlier age and married some Argentinian or some such guy. At the time, she promised him half her inheritence and was stupid enough to write it down. In the intervening years, the husband supposedly dies in an avalanche accident while skiing. Well, now it’s time for the heiress to collect and up pops her alleged husband, waving this written agreement and expecting a nice payout.
Anyway, that’s enough for a zombie thread. 
I remember when I was a kid in the 60’s, the “lost heir” chasers were a common well-known scam, almost the Nigerian bankers of the day. It was somewhat legit. The more legitimate ones did in fact have real estates to give you; they would take the “unclaimed estates” list from various jurisdictions and look for missing heirs. The scam part was that there were others who would ask for a fee up front to see if you were related to the deceased and entitled to the deceased’s estate. The scam of course was that you could be named MacDonald or Smith or Martin and have no real claim anyway, and they would send you a letter and ask for money regardless; whether the searcher knew of a relationship, or made any effort to look for a match, depended on the level of honesty. As long as there was a real pile of money and a reason there might be a connection (name?) it was not outright fraud.
IIRC from items about this, the state held onto unclaimed estates for quite a while, a lot more than 3 years. (7 years? 10 years? 20?)