Sabrent rocket has 5 year warranty if you register it within 90 days, but has to be purchased from an authorized seller, EBAY never has been an authorized seller of any hardware for computers. This is why I don't buy new gear from EBAY and a good chance you get faulty goods or goods that are copies. Drives are the worst on EBAY they are sometimes copies that look like the real thing. Why you think they are a lot cheaper on EBAY ? I think you lined yourself up for a fall sadly there.
Also Sabrent are really good for RMA and send out new drives if yours fails, they don't even question the return, once they get it they send out a new one.
Sorry to say only thing you can do is take it up with EBAY and the seller and ask the seller for a receipt of where he/she purchased it and it may have come from and authorized seller then you could ask Sabrent if they will honour the original receipt if from an authorized seller.