They're big. The people I talk to don't control the policies regarding contracts.
In any case, I didn't lose anything. As long as I get paid for the hours I work, I'm happy. I'd be totally fine with the contract getting terminated tomorrow. I'm also fine with working here for another half year. But at more than a year, I think I'd get itchy.
If we're talking about professionalism, at what point did you bring up to the client that their quarterly contracting strategy leaves them extremely vulnerable to losing critical personnel before the work gets finished? I think what happened there is that they leveraged their project management flexibility against your sense of integrity, and you lost.