If you look at this answer from the bounty faq
What happens if there's no answer after the bounty period?
What happens if I feel my question is still unanswered?
What is automatic awarding?
At the end of the bounty period, if
the bounty starter has not manually
awarded the bounty, eligible answers
can be automatically awarded half the
bounty amount. The criteria for an
answer to be eligible for automatic
awarding are as follows:
The answer must be given after the
bounty was started The answer must
have a score of at least +2 If two or
more eligible answers have the same
score, the oldest answer is awarded
If no answers meet these criteria, the
bounty ends without it being awarded
to any answer, and is not refunded to
the bounty starter.
An accepted answer that does not meet
the above criteria is still ignored by
the automatic-awarding system.
It looks like the bounty was automatically given to this answer by Alex.
This explains why it went to alex. It also explains why no badge for you. Automatic awards don't count because the benefactor badge goes for the "First bounty you manually awarded on
your own question"