It is easy for someone to be tricked into thinking they are validly married when they are not. If you find out that the marriage documents were never filed or that your marriage was never legally completed, you may fall under something called the Putative Spouse Doctrine.
A putative spouse is someone who has a reasonable and good-faith belief that they are married. Putative spouses are entitled to most of the protections that other spouses in legal marriages have. For example:
Dick and Jane decide to get married. Dick gets cold feet and never actually files the papers for the marriage. Dick never tells Jane and they still have a wedding. Dick works at his job while Jane takes care of the children. Years later Jane decides to get a divorce only to find out that she was never married in the first place. Since Jane had a good faith and reasonable belief that she was married. Therefore, she is still entitled to most of the protections that spouses get under the law. For instance, if Dick bought a house while he was married to Jane, Jane would be entitled to half of the house.
The Putative Spouse Doctrine ends when the putative spouse learns that they are not validly married. Therefore, if Jane found out that she was not really married to Dick before he bought the house, Jane would not get half of the house upon divorce.