Not to sound harsh, but what's described here sounds totally believable. Someone who loved Sparrow on Mac wanted to bring it to Windows. He got the blessings of the developer to do it, was even lucky enough to have a few meetings with them.
But none of that implies any sort of formal relationship or gives any reason why the Sparrow team (or Google) should have any sort of responsibility toward him.
It sucks he got burned, but I honestly don't think he has anyone to blame but himself. If you're going to do so much work, either make sure you own the work (and can sell it yourself if the company no longer wants it) or have some legal agreement in place that you get paid for it. Don't leave yourself in a situation where the other person changes their mind and you've got no recourse to recoup your loses.
But none of that implies any sort of formal relationship or gives any reason why the Sparrow team (or Google) should have any sort of responsibility toward him.
It sucks he got burned, but I honestly don't think he has anyone to blame but himself. If you're going to do so much work, either make sure you own the work (and can sell it yourself if the company no longer wants it) or have some legal agreement in place that you get paid for it. Don't leave yourself in a situation where the other person changes their mind and you've got no recourse to recoup your loses.