you need a file from previous patch to do that
you overwrite it n let the game patch again so the games sees you on patch 129
and then the npc option for trade is back again
wich file im not saying :P
They probably used old game files from when you can still trade them in before they patched it used the newest ndreg.xrg and the game will load w/o updating. What the ndreg.xrg does is tells the launcher what version the game is and that it's the most up to date (if the ndreg.xrg is most up to date).
I used to do this back in the days when there were event prizes everyday. I've saved multiple copies of different versions of the 9dragons folder to different places. I would updated the orginal 9dragons folder to the most updated so the ndreg.xrg file is most up to date. Then copy the ndreg.xrg to the other saved copies (make sure to backup the orginal ndreg.xrg for that version) and launch the game from that folder and you have different versions of game files. But you can run into errors if there was major difference like UI changes, skills changes etc.
i think the pplz was made it before the trade was delete. Or have another version some like 129 really idk 
