Historical romance book that I can't remember- guy goes missing and comes back on the day of wife's wedding

The girl initially saves the guy and he thinks she is a boy at first. They get married( i think that the guy is forced into it because of something with the girl's reputation). He goes missing soon after and is thought to be dead. He had met his mistress or previous lover before. Because of this, the girl( who previously idolized him) turns bitter. She becomes quite popular(in society ig because i think the guy is titled) with men. On the day of her wedding to the guy's brother(or cousin), he returns. He misunderstands her. There are two main things i remember: she bet against him that he wouldnt get her ribbon(or something similar) for a race, and that she gave him something of her fathers( a watch i think) that she takes back when she thinks she has been betrayed. The guy eventually finds out from a servant how deeply she had grieved his death till the fact that he met his mistress had come to light. He sets about trying to win her her back

Something Wonderful by Judith McNaught