I think that it was a member called polleke. Go to 'View Players', type in the name and you should find the forum post via his content on Complete Profile.
Help tracking down a sportsmanship discussion please

I've checked his profile: it's under a blog post called Naivety so you may be thinking of something else.

Thanks, GeneralCustard, spot on! polleke's blog. I overlooked the possibility of blogs, focussing solely on forum posts - no wonder I keep losing!
Tunatin: I hope you are, by now, thoroughly ashamed of yourself! What were you thinking? Were you even thinking? (I'm fifth! )

I remember that post. It sure sucked for the player that lost. He said he is cool with the guy that screwed him, but if it was me I'd never talk to the other person again.

My home -> Account -> Manage privacy settings -> Blocked users.
On another note, it would be potentally helpful if members were alerted whenever their name was mentioned in a topic or blog - perhaps that posting could be added to their list of tracked items. To make it easier to implement, the reference to the member would need to be in the form http://www.chess.com/members/view/NAME rather than simply NAME.

Is there a limit on the number of people I can block? Or will it cope with 252,962? (Chess.com has 252,964 members from 236 countries!) I'm probably not allowed to block myself - and I should leave at least one other person unblocked so that I can find an opponent.

That incident didn't happen to me, but shortly after it was discussed, someone asked me to let them takeback their move because it was unintended. I asked them which move they had intended but I didn't get a reply; they weren't looking at the game since it was my move. I messaged them the question; still no reply. Finally, with my time running out, I took the unguarded piece.
I do think electricpawn has a point: if you know and trust the opponent, you are more likely to accept that the mouseslip was genuine.
Can anyone point me to a topic discussion that went something like this:
player A said that he had made an unintended move. Would player B agree to rewinding the board to undo the move?
player B agreed - and made a neutral move which meant that he did not take advantage of player A's slip.
player A then made a different move from the one he had proposed - taking advantage of player B's co-operation.
As a direct result, player B lost a major piece. player B was not best pleased.
THANKS IN ANTICIPATION.