Under standard interpretation of how the bounty system is supposed to work, if a week passes and the bounty is not awarded then half of it goes to the highest scored answer that has at least a score of 2 and was posted after the bounty was assigned.
In the new system, because anyone can post a bounty any number of times and you can post a bounty on someone else's question, this mechanic has changed somewhat. While the scoring is the same, the award counts any post that had been posted after the very first bounty assigned to that question, instead of the time that specific bounty was posted.
Test case can be seen here - the two bounty rewards from Community are when S.Mark and myself each let the bounty expire.
It's even rarer of a case than my last bounty report, but still something that could take a gander.