can someone get away with saying they never got the product x ?
No, but they
can get away with returning the product while claiming it is defective, and they can obviously prove they returned it. They get their money back and you get your product back, so everyone's even. Except for your bitcoins, of course, which you'll never see again. Oops.
okay so I've been through the chargeback process on both sides and here is how it works:
person files a claim with their credit card company or bank. The funds are immediately withdrawn from the merchants account and placed into a temporary holding account.
the merchant is mailed a letter from the customer's cc company with space to reply with a written rebuttal. If the charge back is fraudulent, the merchant will provide evidence like a signed proof of delivery or a merchant slip with the customer's signature on it. If those things are located, then the merchant does have a chance to argue against the chargeback and have his funds recovered
It all depends on if there is a service being used around the transaction like Amazon, paypal or ebay. People who lose on chargebacks involving those companies have lost because it was expressly prohibited to offer the sale of those types of goods according to the terms and conditions set forth on the website and thus the seller typically has zero recourse.