rants&venting ! is there rules for selling items here?

ok ok look here. i got the linkage off of another member on here whos name wont be said and he told me it was complete. and it was 30 dollars shipped. i was not aware there was any missing pieces to this linkage or i would have told the buyer that im not here to rip people off. i was told it was a complete kickdown linkage and thats what i said it was when i sold it NOT knowing there was a piece missing. and i sold it like 3 or 4 months ago and he just now wants a refund i mean come on a deal is a deal am i right? im not being a asshole or trying to f*ck you out of money i was not aware there was a missing piece geez. and i know what all you others are thinking well it should have went with the car yea it should of but i sold it way before i had thoughts on selling the car and i had just got the 383 so i figured no use for a 38 kickdwon so i sold it then a few months later after the linkage was gone i then decieded to sell the car. look im real sorry there is a piece missing not my fault i was told it was complete