Maybe you could use some of that money you're supposedly "saving" by having the work done in China to get in touch with a more local manufacturer who might cost more up front but would also feel some responsibility to meet their promises.
And just to add insult to injury, now they have your idea. If its a good one you'll see copies of it on the shelves in weeks, regardless of any agreements you might have thought you had.
Sorry. No pity here. And no help either. Your story is just another of hundreds just like it that I personally know of. Good luck.