what he did was negligent.
for instance, i made a deal earlier this week to send an olivia voldaren plus some. of course i made this deal in the hubbalabub after a weekend worth of trading when rtr came out officially. stupid me, i fucking traded them off, AND i accepted a dudes trade for em on here.
so i BUY him a new one on tcgplayer. no ifs ands or buts about it. dude didn't even have to ask.
my general feeling for this type of take-back/indian-giving behavior (no offense) is that we MUST be strict against it. our word is all we have to go on. PERIOD. we can't obstruct that passage of consideration for one another otherwise the system becomes broken.
As soon as you hit that accept button, the cards are no longer yours IMHO.