I do know of such a couple. The Mitzvah is called “Machzir reshuso” – returning his property, which, frankly, seems rather demeaning to me. And to do it after accusing her, falsely, of the most disgusting acts too!
Since a man can halachically marry more than one woman anyway, he can remarry ex even if he married in between. A kohen cannot marry any divorcee – even his own ex.