If you award the bounty manually, it goes to the answer you selected.
We can see in the revision history of that question that you chose the higher-voted but not accepted answer to award the bounty to:
Bounty Ended with jwodder's answer chosen by Vogon Poet
occurred 12 mins ago
If that wasn't the answer you meant to award it to, then you misclicked. No system is immune to user error :-)
Bounties can be awarded automatically, but that's not what happened here.
From the main meta FAQ about bounties:
Approximately 24 hours after the end of the bounty period (once the grace period ends), if the bounty starter has not manually awarded the bounty, the bounty may be awarded automatically.
If the author offered the bounty, and accepted an answer that was posted after the bounty was started, that answer is awarded the full bounty.
Otherwise, all or half of the bounty is awarded to the highest-scored answer out of those which...
- ...were posted after the bounty was started, and
- ...have a score of at least 2 (at the time the automatic awarding takes place), and
- ...were not written by the bounty starter.
If the chosen answer was accepted by the question owner, it will receive the full bounty. Otherwise, it will receive half the bounty. If two eligible answers have the same score, the older answer is chosen.
If no answer meets any of the above two criteria, the bounty is not awarded to any answer, and is not refunded to the bounty starter.
However, in this case the full bounty was awarded manually by you, so none of this actually happened. I mention it only in case this meta thread will be useful in future to others confused over the bounty being awarded to the 'wrong' answer.