Its part of the experience as a bounty hunter. In my case, I have not been paid in half of the bounties I joined especially when I was new and joined any campaigns I find. But now im more particular in joining bounties and look deeply to the project and the team running it.
I agree. There is no way for you to quit when you experienced to being pay from your effort or the project just a scam. We should learn from it and search deep about the project. Do not choose easily the bounty and never believe on one information. Do not quit but instead do much better and improve your analyzing skills. I received a reward but never been listed in exchange but still I am hoping for it to be valuable.