Wash. Rev. Code § 11.76.243
If no person appears to claim the estate within four years after it is delivered to the county treasury, as provided by RCW 11.76.240, any heirs of the absentee person may institute probate proceedings on the estate of such absentee within ninety days thereafter. The fact that no claim has been made to the estate by the absentee person during the specified time shall be deemed prima facie proof of the death of such person for the purpose of issuing letters of administration in his or her estate. In the event letters of administration are issued within the period provided above, the county treasurer shall make payment of the funds held by him or her to the administrator upon being furnished a certified copy of the letters of administration.
RCW 11.76.243