I've never seen it happen before until recently. What should happen if you post a bounty on your question and no one answers after 7 days. I think you should get your bounty back but I'm biased :)
I would like to see what others think.
This is answered on Meta.stackoverflow.com: What happens if there are no answers to a bounty question?
this is covered in
In any case, you will always give up the amount of reputation specified in the bounty, so if you start a bounty, be sure to follow up and award your bounty to the best answer!