The marriage certificates are not filed in courts in WA. RCW 26.04.090 (Certificate for files of county auditor and state registrar of vital statistics — Forms) specifies: "A person solemnizing a marriage shall, within thirty days thereafter, make and deliver to the county auditor of the county wherein the license was issued a certificate for the files of the county auditor, and a certificate for the files of the state registrar of vital statistics."
If you do not want any dispute as to the validity of the marriage and the exact date of the marriage is not important, the surest thing to do likely is to go through all the procedures and get married again.
If the purported nonspouses do not want to be married with each other and do not dispute that there was no marriage, likely there is no one else with legal standing to file a court petition.
The answer depends on the specific facts. You should review your specific facts with your attorney to find out your legal options.