Now you may think that the one that got away will return one day, because you are soul mates. But that is not always true. Regardless of the connection, all soul mates are given free will to do whatever they wish with the connection.
Now the universe would love it if all soul mates used their connection to grow and elevate themselves and their partner, but that is not always the case. The one that got away may stay away, permanently. Yes, that sucks, and it is not fair. But the universe cannot intervene and force them to reunite with you in a relationship. They can send them signs and throw obstacles in their way, but the choice, ultimately, is up to them.
Of course it is not easy to forget the one that got away. You may think of them all the time, and find yourself unable to move on. Well, you have a choice just like your soul mate did. You can choose how you live your life while they are away, doing the best you can to find as much happiness as possible. You can also choose not to move on. Closing yourself off to someone else, and focusing on what you lost, will keep you stuck. Doing so will not support you of being open to joy.
You may have spent years, or even decades, apart from the one who got away, but still find yourself daydreaming of what could have been. The reality is your soul mate chose to do nothing. They chose not to be with you. Is it a bad choice? Are they happy with that choice, or are they miserable? None of that should matter to you, unless they choose to come back. So stalking them on social media will not be a productive exercise.
You have to leave them to their choice, and to reap the consequences and karma of that choice. That may be what finally opens their eyes and heart, and gives them the courage to return to you. Some people, unfortunately have to learn their lessons the hard way. They take what seems like forever to learn what you knew all all along. You have always known the two of you would be great together. But they learned at their own pace, and although it may take a very long time, you can teach old dogs new tricks.