Amazon did something similar to me on a return. I returned a top end pixel book ($1500) UPS said it had been delivered to return center. Amazon said they didn't have it so they weren't going to issue the refund. Despite my receipt from UPS. I did a chargeback, and lo and behold the next day they sent me an email saying they were issuing a refund.

My experience would match lixtra's either get an attorney or write it off, they're punks about this sort of thing.