But, if after you've made diligent efforts to locate your spouse and can't find him / her, you can ask the court for an Order of Notice by Publication. (rocketlawyer.com)
Yes, it can require diligent effort, but it's well worth the time and trouble, especially since your competition might not bother to do it. (thecareerexperts.com)
Of course, this can be easier said than done, but it is entirely possible with diligent effort and research. (exclusive-executive-resumes.com)