In Texas, you can divorce a spouse even when you don't know where they are currently located.
I usually recommend that you try to find the person first. Look on www.facebook.com and other social media sites. I usually don't recommend hiring a private investigator because the attorney appointed will have to repeat all the work done. However, occasionally a pi can find the person so if you have the money to spend you might try this first.
If you can locate the person, it definitely saves you time and money.
If you truly cannot find them then hire an experienced lawyer to help you. I think it's too complex to try to do it yourself. Of course, you can try but I think you will find it frustrating and difficult. It might not be impossible but I don't see any pro se (self representing) parties successfully complete such a case when I'm in the courtroom.
If you cannot serve them personally then a "publication divorce" will be necessary. It needs to be published in an appropriate way and then the person publishing returns a certificate to the court's file. Merely publishing in your local paper is NOT enough. You MUST have the certificate of publishing filled out by the newspaper.
Then the judge will appoint an attorney to represent the interests of the missing spouse. YOU pay for this. I normally charge around $750 if I am appointed on such a case. Some attorneys are less and some are more. But normally $1,500 is the highest I've seen it go unless there are unusual circumstances.
The attorney will normally talk to you or send you questions to answer. This information will help the attorney find the missing spouse. Often people don't realize how much information they have on their spouse that can help locate the person.
What do you need to help find the person?
Full legal name
Other names used
Date of Birth
Location of Birth
Social Security number (even if it's made up - I've found people)
Driver's license number
Career info - (for example - a barber - that requires a license)
Where are the person's parents and/or siblings?
Who is the person's best friend?
Last known address
Last known phone number
Last known employer
Where did they go to high school and/or college (many alumni groups keep info on their alumni)
Photo of person
Where and when did you meet your spouse
Hobbies of the missing person
All social media presence
Criminal convictions (I've found some spouses in prison or jail)