Wow that's crazy

I just wanted to state the fact that it was OP's mistake and let OP know how this kind of a mistake could have been avoided / can be avoided in the future. That's all. No admonishment or anything like that. I didn't mean anything bad to OP.

And yes, I can see this kind of a mistake being more likely to happen to a newcomer than to an experienced HUT player.

Nor are there safe guards for making sure these mistakes don't happen.

I don't think it's even possible to make it 100% sure that mistakes like this don't happen. As it is, when you hit the confirm button, the game asks you if you are sure that you want to confirm the set. In addition to this, EA could probably change autofill so that it would be less likely to use cards that you don't want to trade in, but I don't know what else they could do. And it would still be possible for autofill to use cards that you don't want to trade in.

Whatever EA does or doesn't do, the best way to avoid mistakes like this is to always check the cards that were autofilled to the set instead of just blindly confirming the set. Even if you are assuming that autofill won't use any cards that you don't want to trade in (for example in this case I can understand why OP didn't think that X-Factor Kucherov would be autofilled to the set), you should check the cards before being sure that you want to confirm the set.

Like EA taking higher rated cards instead of base.

No, autofill doesn't use higher overall cards instead of lower overall cards. It might use more valuable cards instead of less valuable cards, but not higher overall instead of lower overall. But if you are not referring to overall when you say "higher rated cards", then I believe the quoted sentence is true.

And as a last point. You are counter minding your previous point by your last statement. You hold the individual responsible. Then you question why.  ?

I don't quite understand this. The last point was about whether or not EA is technically able to return an accidentally submitted card. At that point the mistake has already happened, so I don't see how the last point would be against the previous points. And it was just speculation that EA would technically be able to return an accidentally submitted card. I don't know it for a fact and EA_Aljo hasn't confirmed it. But even if they are technically able to do that, accidentally submitting a card and EA refusing to return an accidentally submitted card are two different things.