No, they don't have 'the one who got away'. They have a fantasy about someone who they don't have to deal with daily. That kind of relationship is very easy to maintain...in your mind.
My wife and I have been together 4+ decades and she still amazes and amuses me daily, without even trying.
Recently, I overheard her BFF ask her:
"If your husband passed away, would you remarry?" She said, NO, do you know how long it took to train this one"
Of course 'train' meant my willingness to be kind and considerate at all times, my goal all along. As she does.
Signing off. I'm going to see if she needs a coffee refill