Hi.

I hate to be the one who says, "I will never shop at your establishment again" threat rarely works.
They honestly don't care about one person; and,
rarely do we keep our threat/promises. Either render the threat useless.

Another issue raised by others, and the first thing I thought, was "How does Target know you didn't?" They don't. They simply know the item is not in sale condition, you have it, and therefore, posession is 9/10 of the law.
About the only way you can explain your position successfully, is to demonstrate that it is unlikely you had time to change things, and run back to the store.

I've learned over the years to inspect packaging carefully. And, if possible, to open the item, and make sure it contains everything its supposed to, etc.

And, while you might not even consider doing such things, as having been explained, not everyone has a solid moral character. I remember attempting to explain to Best Buy that a Visioneer scanner they had placed on the "opened items" section was wrong. They of course did not want to acknowledge they had been taken. But, it didn'take a genius to realize that the model the scanner lid had was not the same model it belonged to. Unfortunately, someone had purchased a newer model, and exchanged it with their older model, and simply exchanged the covers. Since they were the same, it didn't matter to them. The only difference in covers, was model numbers. But, in the models? the more expensive model had more buttons, more features. So, yes, people do this. And, in all honesty, they will make the same claims. And, stores dont want to take the loss. That's for sure. And, of course, we who get ripped off don't want to get stuck either.

Sadly, someone will lose on these propositions. Therefore, let me again, strongly urge you to pay attention to the packaging. That is really the best way to protect yourself. You can't count on store employees doing their job correctly. Which is how these things happen to start with.