Proves too much; would justify (as others have observed) opening a Rolex box and taking the watch out on the theory that the store didn't "find" the watch, only the box. Or stripping the lining out of a jacket on the theory that they still have the jacket. That can't be the right result.
More fundamentally, this is a stupid argument, and dangerously close to the vortex of the "morality of thrifting" argument we've gotten mired in too many times. Let's stop and get back to posting pictures.
Yeah, horrible, horrible example. With a rolex box, the rolex inside is expected and obviously integral to what's being sold. And the lining of the jacket is an integral part of the jacket- something found in a pocket isn't. You can't take the item for sale or part of the item for sale, obviously, since that compromises the sale for the store.
It's not abandoned property unless some customer after Goodwill bought the jacket accidentally dropped the bill in (matching the money on the floor market). If the money was in the jacket when Goodwill got the jacket, it's Goodwill's.
To argue otherwise would be like suggesting that you can drill oil on someone else's land if they haven't noticed they have oil underneath yet. Your property rights are complete, not just what you notice you possess.
EDIT - Oil is actually a terrible example, since some states do have (or have had) systems where whoever gets it first gets it (Eiliff v. Texon Drilling Co., 146 Tex. 575, stupid first year property) but you get my point.
Nobody's disputing that you can pick up a bill (or let's just say a quarter) off the floor of the goodwill, even though goodwill owns or otherwise controls the store. It's inside their property, so it must be theirs, right? What makes that so different to you?