1. If you don't brush iOS7 or below, you still can't find your iPhone through iCloud, because if you don't brush iOS7, you can log in to his own Apple ID again instead of using your Apple ID, and you can't find your iPhone through iCloud.
2. If you used to be iOS7, and the thief is also iOS7 after brushing his mobile phone, then he needs an Apple ID account and password to turn off the function of searching my iPhone or erase the device. Even if the information on the device has been erased, finding my iPhone can still display customized information. People who want to reactivate the device need your Apple ID and password. In other words, your iPhone is still your iPhone, no matter where it is.
Of course, if he brushed iOS7 and found it useless, it might be useless to throw it there. Your account may be offline, or your information has been tampered with by other hackers.
Judging from your description, 1 is more likely.