No, points placed as bounty on a question are not refunded in the event that the question receives no answer. 

On the reason let me quote myself from   [another discussion about the merits of refunding bounties](http://meta.mathoverflow.net/questions/1976/bounty-policies).

>The reason that a bounty costs points is two-fold. On the one hand the points are a direct incentive for somebody to answer. 
Yet, on the other hand, the bounty **gives significant additional visibility** to the question. 

>The second point seems at least as important as the first one. It is this additional visibility for which you have to "pay" no matter what. 

>Bounties need to "cost" something to stay effective. If they would be free, somebody could put a bounty on essentially unanswerable questions all the time, under-cutting the effectiveness of  bounties.

>You could think of a bounty like an advertisement. One normally has to pay the newspaper, the radio station or whatever medium irrespective of the effect the advertisement has on ones sales.