@WizardJeremyArch Perhaps the code was already added to your account? If your Origin library was updated to reflect that you now own the limited edition of Supernatural, that will also apply to your store account, which uses the same information as Origin. You can login to the store site (https://store.thesims3.com/) using your Origin credentials and check your purchase history; the pea shooter should be listed there.
If the item hasn't been added your store account, it's probably best to contact EA customer support again and explain that you're still missing the store content that comes with your limited edition EP. EA will have a record of your previous help request, so it should be simple to resume the conversation where it left off.
@WizardJeremyArch Do you by any chance have more than one account? Another reason your store page wouldn't list an EP that your Origin library contains is if there's a lag in adding a new purchase, but that's usually a question of a few hours, or maybe a day.
I suppose it's possible that the EA rep who helped you removed your already registered copy of Supernatural from your account without replacing it. But players redeemed the Limited Edition with a second code; I was under the impression that the pack codes (as opposed to the bonus ones) were all the same. Regardless, it sounds like you'd benefit from having someone at EA's end take a look at your account. There's no way anyone here can see your account details, much less update them.
