You have to choose the bounty that has a good and reliable manager. If you are feeling depressed that your efforts were wasted that's the other side of bounties.
If they aren't able to reach their soft/hard cap they will never pay your efforts so if you want to get paid with the bounty you are joining. Just choose the bounty that has an experienced bounty manager and assures the participants to get paid.
I do agree. Such unfortunate scenarios are always possible to happen and that is why bounty hunters should be mindful on the programs that they would particioate with. Not all bounties or projects would be all profitable as what it is expected to. Changes do suddenly happen due to market volatility which might appear to be unexpected by the team behind a particular project.