This thread had a bounty of 150 on it ...
My answer was accepted a day or so before the bounty finished and I note the user has lost the reputation. On the other hand I never received the bounty. Why is that?
Because OP didn't click +150 icon under it, and you don't have +2 upvotes to get half bounty.
Bounty rules changed, and accepting an answer does not automatically award bounty anymore.
The implementation has changed a bit to better accommodate careless bounty owners. :)
... then we assume the question owner liked your answer when they accepted it, and it gets the full amount of the bounty at time of bounty expiration.
I would probably guess that they only accepted your answer but didn't assign the bounty to you. And you won't get half the bounty automatically as you need at least 2 up votes