Just as an aside, I worked part time at a retail chain similar to Wal-mart to pay for school and specifically handled receiving/stocking. The way you're describing it (having to *look up* release dates) is not what happens.
You receive a box from UPS/FedEx/whatever. This box is marked "DO NOT RELEASE UNTIL [DATE]" with big obnoxious stickers in bright colors, ours would usually be orange, and usually arrive a week or a few days in advance. You open the box, add the contents to your inventory and tag/prep it for sale, put the inventory *back* in the box, *SEAL* the box, and put it in a designated area to be stocked for the release date.
This is not confusing. The product ends up on shelves early due to A.) employee incompetence of just grabbing boxes to stock and ignoring the GIANT ORANGE STICKERS or B.) employees being *told* to stock it early, which is usually the case for big untouchable chains like Wal-mart. When this is the case, it is almost always on a weekend so that smaller retailers have a harder time contacting their distributor for permission to break release date as well, and Wal-mart has several days of exclusively selling the product.
This is a bad thing, because it absolutely costs smaller businesses a ton of money because they can't risk going against their distributors. If Civ 5 didn't have a lock on it, how many fans would rush their Wal-marts to see if it's for sale, and cancel their pre-orders? A lot. And you also get cases like this, where the customer is upset because s/he has a product that can't be used due to being sold early or doesn't have a day-0 patch available, etc, etc. It sucks for everybody but Wal-mart, basically.