True. And regardless, it's reasonable to still be very irritated. Now at least two people have mallards that they're attached to when what they wanted was call ducks, and that puts those folks in a hard position, deciding whether to keep the "mistake" babies or not. Even getting your money back won't fix that problem.
Still, you won't know whether they'll try to help you unless you check with them. I still think it might have been a mistake, because they could have labelled a large batch of eggs wrong, and then the mistake would easily have been perpetuated when they divided the batch for sale. It's likely there are more than two victims, too.
If they are good sellers, they will quickly offer your money back with an apology and an offer of something extra to make up for your time, the hassle, and the emotional aspect of it too. If they don't do that, then you'll certainly want to take it to the next level, because you obviously did not receive what you paid for!
Actually, if they're *really* good sellers, they'll identify which batch was mislabelled and pro-actively contact everyone who received eggs from that batch and offer to make up for the mistake.
In any event, I hope it works out for you. I'm sorry you're having to go through it.