Personally, I think the OP was quite clear in the order of events. I work as an investigator and an interviewer. The randomness of your roommates son buying the same exact (and very expensive) tablet that most people don't own (hence even the lack of development) is pretty..... well, random. Listen folks... This chick stole his tablet. She was careless and left the manual laying around. If you don't think that's the scenario then you're naive. I had an iPhone stolen from my house and about 3 months later saw a friend who attended a party at my house using MY phone with the same case and the SAME exact old sticker residue on it. He told me that he bought it from a coworker. I snatched it out of his hands and he just walked away without a word. Haven't seen him in my circle of friends since.
The best that you can do is hope that she messes up and flips wifi on. Or, you can ask her son about a feature that you don't quite understand the next time he's there and then wait for weird looks. If sucks for you because Amazon has now added you to a list of potential thieves. Retailers deal with people saying they never "received"an item all the time and is not always legit.
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