Did you also check the price tags attached to each piece? Those would help to clear up the price. There might have been a really good sale, but a quick check of the price tags would have aroused suspicion that this was too good of a deal.

The website indicates that the fleece hoodies and capris are $19.99 each. I clicked on "Fleece Sets", but each piece was clearly a item.

The main lesson you taught your daughter is that it's better to be quiet and be overcharged than to politely point out the discrepancy. You showed her that it's more important to avoid embarrassment than to be charged more than you expected.

I have said, in front of my teens and other customers, "Are you sure that's right? Oh, I thought those were on sale." I have made a split decision to either pay or ask for the item(s) to be removed.

It's also not hard to pay, then turn right around and get back in line to return the item or speak to a manager.

Your 12-year-old "loves" the store and "likes" the clothing. It seems to me that you have dealt with Aeropostale before, and you would be wise to how they set up their stores. New, seasonal items are in front on attractive displays. Same with staples like jeans.
This is where you go to find the hot new looks for the upcoming season. (Then, as a smart shopper, you go to Kohl's or Target and purchase similar styles for less.)

The clearance items, which can often be worn year-round, are on the side walls in the back. My 13-YO daughter knows that if we're buying something with an Aero label, it will be from the clearance area. In fact, I ran your scenario past her. She came up with the same answers I did.

If you still have the tags on the items, you can easily take them back. You still have the receipt. It's probably too cold in Columbus to wear the sweat pants right now anyway. Teach your daughter how to be a careful shopper.

Also, a small quibble: Your letter is sent by "Deanna", yet you claim that the cashier called you "Sir", and you refer to yourself as a "schmuck". To me, "schmuck" indicates a male, not a female. (But my Yiddish is pretty non-existent.) Are you Dad or Mom?