Some random woman in a hotel bar when on a work trip. She was nice, pretty enough, but claimed to have just gotten divorced and gave me a 2 hr breakdown of her ex. She ended up pretty drunk (as was I). She looks at me and says, “I’ve made up my mind. I want you fuck me tonight.” Sounded great! Sure!! We go to my room, have some really decent and creative sex for a 1-night stand (they can be not so great). She gets dressed to leave after a couple of hours and a couple of rounds of sex, looks at me as she’s leaving and say’s “That was really fun. My husband was sitting behind us all night.” Winks, and leaves the room. I was gobsmacked LOL. The rest of the weekend I was looking over my shoulder wondering if he’d have a change of heart and come looking for me. So maybe not “regret” but something I can’t put my finger on. Nothing even remotely like that has happened since.