For reasons still unknown, Apple appears to have removed the Activation Lock checker that was previously available via iCloud.com. That tool, which used a device's IMEI number to determine its Activation Lock status, provided buyers a fairly straightforward way to spot stolen devices.
For example, a thief with a hot iPhone might list it on Craigslist or Ebay for a rock-bottom price, the idea being to sell it quickly. But if the phone is still locked to the owner's account, you won't be able to do anything with it. And without the Activation Lock checker, you can't determine that status before buying.
However, all is not lost. If it's an online purchase, you can still ask for the IMEI number and use one of the carriers' checkers:
Sprint's bring-your-own-device page mentions an IMEI checker, but I couldn't find anywhere to actually enter a number. Fortunately, there are third-party IMEI checkers available, too, like this one from electronics buy/sell service Swappa.
It's important to note, however, that although an IMEI check can help you determine whether a phone is stolen, it won't indicate whether it's still locked to the previous owner's account. Indeed, I believe it's entirely possible for an IMEI to show up "clean" while the iPhone or iPad is still user-locked.
Consequently, Apple offers the following guidelines when buying a used device:
When you buy an iPhone, iPad, iPod Touch, or Apple Watch from someone other than Apple or an authorized Apple reseller, it is up to you to ensure that the device is erased and no longer linked to the previous owner's account. Follow these steps before you buy the device:
- Turn the device on and slide to unlock.
- If the passcode lock screen or the Home screen appears, the device hasn't been erased. Ask the seller to completely erase the device by going to Settings > General > Reset > Erase All Content and Settings. Don't take ownership of any used iPhone, iPad, or iPod touch until it's been erased.
- Begin the device setup process.
- After choosing a language, choosing a country or region, and connecting to a network, the device will begin activation. If you're asked for the previous owner's Apple ID and password, the device is still linked to their account. Hand the device back to the seller and ask them to enter their password. If the previous owner isn't present, they can remove the device from their account by signing in to icloud.com/find. Don't take ownership of any used iPhone, iPad, or iPod touch until it has been removed from the previous owner's account.
You will know that a device is ready for you to use when you're asked to "Set up your iPhone," "Set up your iPad," or "Set up your iPod" the first time you turn it on.
Shorter version: Only buy from someone you can meet in person, and take the time to actually go through the setup process before handing over your money. If you've had any experience buying used devices -- good or bad -- share your thoughts and tips in the comments!