wow, the OP really is just not a good person. This country is slowly going downhill, people like this do not help the situation.
1. It does not matter if the company is large or small, it's not yours, return it. Trying to use the excuse that it is a large company just to make yourself feel better is crap.
2. It's the right thing to do.
3. It is not your property and it belongs to someone else. Let's say you sold something on eBay and something worth $600 happened to fall in the box and you didn't realize it and didn't know where it went, would you want that person to send it back?
4. Every device that goes missing out of inventory helps to drive the cost of the product up. We pay enough for stuff in the world today, don't contribute to the problem.