People buy and sell iPads and iPods all the time. The ones that are out the box are the ones to be worried about as those may have belonged to someone. So it would be different if it came out of somebody's house, car, bag, etc. then it would register as stolen. So take it to a Apple store and if they tell you it's stolen tell them you got it online or through one of those pop ups that always seem to have the iDevices cheap. (Good luck. I'm not responsible for the advice I just gave, and I won't be held responsible for what happens in any way.)
I disagree. If you ever, EVER get caught up in a problem like this, always get your story on the record. Do not let the authorities start asking why you did not tell the truth.
You can do nothing and keep the device, but that is wrong, or you can call Apple with the device serial number and ask a few questions, and that is the right thing to do. I think you should call or email Apple directly and tell them your tale. Ask them if they can find out if the device is hot or not. If they say no, keep a copy of your email to and from Apple. The Apple wonk that answered your mail could be wrong or perhaps to get rid of you, he or she just tells you, it is not stolen.
Frankly, I would not trust an Apple store employee because you never know what can happen. For example, they call the police or keep the unit.
If you do make an inquiry, do the right thing and tell the truth if asked. Do not make up a story. You want to be on the record in case this thing comes back to bite you. Perhaps the thief implicates you or perhaps the seller is part of a larger ring and the police have been looking for leads. Thieves often toss people over the side of the boat to save themselves and you just do not know what can happen. Especially if this thief is part of a bigger story.
You bought the device in good faith and you think it is hot and you want to do the right thing. Do not screw yourself by getting caught in a little fib. Learn the lesson and take the loss. Perhaps Apple will feel sorry for you and rewards you for your honesty.
I am a paranoid old sot about this sort of thing. I am not a lawyer, but apparently you suspect it is stolen and mere possession can get you in trouble. Especially with a hot product (Are iPads still hot these days). If I were a cop, I might not listen to your excuses because you should know that a cheap iPad in a box, unopened (right?) would not be sold at a deep discount.
But that is just me. I have lived long enough to know sometimes decent and innocent people are caught up in something that quickly goes very bad. I know a simple and innocent thing can grow and become very serious. What if this person you bought the device from stole it during a robbery in which someone was hurt or killed? But that is just me, a true paranoid. You need to sort this out now.
So . . . You are not sure if the device will be discovered when you sync. You posted here asking for help because you are concerned and now there is a record of our conversation. There are penalties associated with receiving stolen property. Lots of problems, you now think. Do yourself a favor and clear this up today. Otherwise, you will be sad and stuck with a device you really cannot use and you will fear every knock at the door or every police car that drives down your street.