If someone asks you for marriage and they disconnect before you accept, then you accept, it doesn't show up as you two being married, but in your friends list there's a heart next to their name and it still gives you the message saying you're married to them..
http://gyazo.com/24d5f4505f62f66ed78b01d7a488dc00

Edit: It says you're married to them on their account, but not yours.