Seems like a classic case of caveat emptor here. Am I understanding correctly when I say you bought the gears, didn’t check them but then also sold them without checking?
You can always ask for your money back (assuming you are able to reach him) and in an ideal world you would get a refund. Given that it’s been two years you are unlikely to entertained by any reasonable seller who sold them in good faith, let alone someone who might have been intentionally disingenuous.
Really it comes down to a question of how much hassle/stress/time the money is worth to you. I’m with the Chris’, chalk it down to experience and move on.