The way we do gifts in my family has been that way since before I was born. It's just the way we do things. You may not get that family tradition, but each family has their own ways of doing things and that's ours. No one has to participate, of course... but it's understood that, if you do, you follow those two rules, you spend the agreed-upon amount, and you shop off the list, unless the person doesn't make a list or says they just don't care.
If we had a different system (and I'm not saying we shouldn't - this Christmas is a perfect illustration of why that's worth considering) then expectations would be different. As it is, though I find it somewhat frustrating, I'm hardly MAD at the person who gave it to me. But I also feel it's within my rights to take it back and get something I'll use, if I can. If someone bought me a sweater that didn't fit, I don't think anyone would expect me to keep it around just for kicks, would they?
It wasn't an exact item off my list, either. I had about fifteen things on there, all of which were available at just about any mall or general goods store. So it wasn't like she got me something that was just a hair off and I threw a fit. I didn't have anything remotely like this on my list.
I've never had an issue returning anything, with or without a receipt, if I had convincing evidence that something came from that store. On multiple occasions I've lost the receipt or not had one, but had an item that they clearly kept in stock, and had the bag it was purchased in, and they were happy to give me store credit. Those are stores I'll go back to, because they made the shopping experience an easy, pleasant one.
Part of my frustration is what seems to be a litany of small-business issues of late, chiefly businesses that post hours they say they're open, and you make the drive out there, only to find out they aren't open after all. I've had two failed attempts at a haircut in the past month for that reason. And then you read about business owners in the local paper who bemoan that no one patronizes the business! Yeah, we tried, but every time we showed up during your posted hours, you weren't there...
People talk about what a shame it is that so many mom and pop places are losing out to big-box stores, and I agree. I love the local flavor and uniqueness of small businesses. But I've only got so much free time in a day - I have to work for the money I'm going to spend at those businesses. And after I make a couple of trips, only to find out a place isn't open when it said it would be, or that I'm going to have to drive to another county just to get a receipt from someone so I can even get store credit on an item that clearly came from that store and has the pricetag still on it, yeah... I'm done with that place. There are just other options. And that's fair - benefit of the free market.