If he confronts you and you seem legitimately apologetic and confused as he is, there is a good chance he will be more upset with her. After all, if you thought she was single, why wouldn't you pursue her?
Be like, who is your wife? when he tells you be like, Thats your wife bro? I am truly sorry man she said she was single.
After all when she says "I TOLD YOU I WAS MARRIED" you pull out the "No you didn't, your just trying to get your husband after me when YOUR the one to blame here"