Car purchases are monitored on a state and federal level. That is to say, you need to register the thing, which is made MUCH more difficult without a pink slip.
I have always had my receipts emailed to me at the Apple store. Those are incredibly easy to alter and make look believable for a sale on CL. It's not THAT much harder to alter a legitimately printed receipt either.
Which is why it's not a good idea to purchase consumer electronics off Craigslist in cash, instead of using a money order or other method where you have a receipt of your purchase.
The argument here is that someone could sell you an iPhone and then report it stolen. This isn't specific only to the iPhone, but every other consumer electronic that could possibly be sold on CL. Someone could hypothetically sell just about anything on Craigslist with a fake receipt, then claim it was stolen. That's why we have laws against filing a false Police report, and fake insurance claims.
And I think the issue is getting pretty confused here:
Under your scenario, Apple would give you the phone back
So now I have your money and your phone
This is assuming someone is:
1) Dumb enough to buy something expensive off CraigsList in cash
2) Takes it in to an Apple store for "warranty service" they don't even have without getting some kind of documentation from the seller
3) Can't explain to The Apple Store that they bought the iPhone off CL in cash, don't have a receipt, and that the person who reported it stolen was lying
4) They leave the CL-purchased phone at The Apple Store after they're told it was reported stolen instead of talking to the police
5) The police decide the phone was stolen and don't investigate the CL sale
6) Apple returns the phone to the original buyer without any investigation whatsoever
