You can try my plugin
The idea is to give an extra boost to all docs that match a given term with the help of function scoring. If your top doc has a special value which is unique, you can configure a ridiculous high boost value to achieve the desired effect.
I do not recommend 1.6 - please stop using it, also for security purpose https://www.elastic.co/community/security
Please update to 1.7+ or 2.+ as soon as possible.