You do nothing and move on. If you didn't get a stake then you probably didn't do the task right like the instructions told you. There's plenty of bounty campaigns that the project didn't reach soft cap and you won't get paid for that either.
Make sure you read ALL the instructions on the first page, Including the general rules.

And if you done it all correctly the bounty manager could have just missed it (They can make mistakes) or maybe the bounty manager isn't to trustworthy. Try and pick a bounty with a reputable bounty manager.
Don't stress to much there is plenty more to do.

I do like the topic thread you made but, calling out the bad managers by the community is good.