I don't remember a fic where HYDRA sends the WS to do this, but there have been several pre-CA2 fics where the WS ends up seducing Steve for Reasons? My favourite was the one where the WS wakes up alone and decides to get out of Russia so signs himself up as a mail-order bride and Tony Stark orders him for Steve as a gag. And Steve does not say anything about it being Bucky (even after they discover that he's the WS) because it's too weird to explain so he just... doesn't.