Is this a joke post? How do you plug in a riser in the wrong direction? Do you have a pic? Are you referring to the part that goes in the 1x slot?
there are 2 ways to do it.
it had a four pin molex and he put the molex in upside down.
or he plugged the 1x pcie in backwards.
both are possible to do. but the card may have survived and the riser died. or the pcie slot died on the mobo.
If the card was perfectly new and never used and no longer works it does not mean he killed the card.
Since he never tested it and knew it to work he can say it never worked and not be lying if he wants an rma.
He may have just killed off the riser and or the pcie slot and the new card came doa.
It can not be sure if it happened the way I just said.
For instance I have
13 amd 5500
16 amd 5600
15 amd 5700
44 good cards
and 2 DOA asus dual 5700 xt
So if that happened to me on 2 of 46 cards I would not be at fault
and on the other 44 I would be at fault.
Just saying maybe the op has legit wiggle room.
The funny part is riser still works, only the connector to motherboard burns but the pcie slot and riser cable works very well, now the card isn't displaying anymore, I've tried in 5 different motherboards just to confirm but no luck