I’ll tell you what went wrong.
They were cheapskates who didnt want to pay you the market rate, and strung you along with vague promises of profit sharing. They (from what it seems) really didnt have a business model, and wanted a mark to do the work for free, so that they could then go to a VC for more money.
And from what I’ve heard, this is pretty common in the VC world. Hence this is bootstrapped.fm, not screwed-by-a-vc.fm (though I would love to start that )
You need to make up your mind. Are you a consultant, or are you a bootstrapper? You can be both, but not at the same time. And as a simple rule, when you are working on someone else’s business idea, you are an employee, and nothing more. So you get paid like one.
You are lucky to have escaped what was clearly a con at extracting free work from you. Learn to respect your time, and yourself. Because you’ll be meeting a lot more of these “Startups”.