Facebook – Knowing who I sent a friend request to on Facebook

According to this Facebook topic it seems like there's no way of retrieving the message that was attached to the friend request.

As a last resort, if you have the original notification email still in your inbox, the message might be there?

You can view the requests that you have sent using this app: https://www.facebook.com/PendingFriendRequestsApp

You can't view the people that have declined your friend request. Also remember, if you get a friend request from someone and you decline them, facebook will ask you if you know the person outside of facebook. If you choose no, facebook may block the person from sending out other requests for up to a month. Obviously, this can be done to you as well, so if someone has not accepted your request you might consider canceling the request so you don't get blocked from requesting.