I know exactly what's going on here. This is related to survey caching in your account -- and the good news is there's a super easy fix! If you ever notice that the system hasn't updated to move beyond that last cached survey list, to get that to refresh, you'll just want to create a new "dummy" survey and publish it. You don't have to do a thing to the new survey besides clicking to create it and then publishing it. Once the new "fake" survey has been published, if you go back to your mailing, you should see the full, correct list of survey options in the link dropdown.
I've gone ahead and done this in your account -- I just created a fake survey called Emma test -- and now you have the "2014 Survey for Leaders Feb Mar Apr 2014" survey option in your link dropdown when you're setting up your mailing.
Hope this helps! Please give me a shout here if you're not seeing that survey option in your link dropdown or if I can provide any further clarification on this.