I don't think he said that he's been cheated but about failing it, he did said that. He was just disappointed that he didn't claimed it before and yes, no worries with that as he has seen that those codes already expired and he has to move on already. Anyway, you're right with all that you've said and there's a need for them to be attentive at all times especially when they've been joining giveaways and contests for them to see if they've been rewarded or not.
If that's the case, then it's only the fault of the person who was late to the giveaway. It happens. Why complain about such a circumstance? You didn't make it. Why do you have to make a global problem out of it and curse everyone? It's not worthy of a gentleman. On the contrary, I would just keep silent and draw conclusions from my mistakes, so as not to repeat them later.
Some people just draw some conclusion that they are still eligible with payments for past win they get. But these people fail to realize that its their fault why their winnings got voided since they are the one who didn't claim that's why they can't do anything with that case but try to learn from that experience.
If that case happen to me I will not create any noise but will just regret those happening privately since creating commotion on someones thread will not change anything. Hopefully he learn from that wasted opportunity that he experienced.