When your spouse has disappeared it is a fact that is actually not a problem in that the court can be approached for direction as to how the divorce summons should be served. If your spouse has disappeared, the court will direct that the summons be served by way of substituted service so it may direct, e.g., that it be served on a relative of your spouse or by way of publication in a newspaper that your spouse used to read.
If the person who is considered to be your spouse lives overseas, the court will give an order that it is served on him or her personally at her place of residence or work. This is called service by edictal citation. It may be that your spouse lived overseas but has since disappeared, the court will give directions as to a form of substituted service, e.g. by service upon a relative or, perhaps the lawyers that used to act for him or her in South Africa and elsewhere, or in any other manner.
You will have to satisfy the court that you have done everything possible to track your spouse and it doesn't matter where he or she has disappeared. And you will have to provide your lawyer with certain pieces of information, such as your current place of residence, your job description, date and place of marriage, details of children born of the marriage, etc.