Thanks for the advice everyone. The store manager and police resolved the problem and refunded me the money. I took money instead of another iPad 2 from the store because I going to buy from the apple store online.
I called the police first last night and got them to come to my business suite. When they met they said I should go to the store first (like many of you said), but they said they will accompany me. When we were there about five or six people were involved excluding the cops. They spent about one hour viewing video tapes from the store.
The female general manager explained that one customer bought two iPads and returned one of them. The iPad WAS NOT checked when returned, and the manager explained that was not procedure. If the item was opened they send it back to the manufacturer ( Apple I assume). They thought it was unopened so they put it on the floor again. There is a report now, however, the customer they tracked paid cash.
Thank you all for the kind replies. To all the people who doubted the situation, it took five minutes to sign up for the forum and post the pictures while I waited for the police. I don't know how long it takes you to post pictures on a website but for me it's quite easy. It is quite sad the skepticism and pessimistic views of the world and of people. And have you ever held an iPad 2 box with an iPad 2 inside? Yes. That's how much it weighed. Not that hard to comprehend.
Again, thanks for your help. I posted for ideas for anything I can do in addition to what I have already done. It was more of a brainstorm to see if I missed anything in the process. The store manager wanted to assure me that it was not a walmart employee that acted like so and walmart was very professional in that regard and secure in their important products. Definitely writing a thank you letter.
Edit: the manager also confirmed that the shrink-wrap was not standard of apple products. I should have known better seeing how I have bought an iPad 2 before.