If you do not have a living trust (highly unlikely anyone would hold an offshore betting account in the name of a trust anyway), it is probated along with everything else. The heir(s) should report the asset (offshore account) in the estate inventory list, and the probate court will eventually issue an order allowing the heir(s) legal title to the asset (offshore account). Now whether a Costa Rican corp. will recognize the Order as bona fide (legit) is another question, but I would think most would be accomodating under the circumstances.
If nobody is aware of the asset, your heirs are SOL. If in the U.S. the asset will eventually escheat to the State (state rips it off) after "reasonable" attempts to locate heirs are made. If the asset is offshore, well, I don't think there is anyone who can't figure out what will happen in that situation. Call it christmas party money for the offshore sports books.