[H4CK3RM4N]

It's configured with an account at setup. You need to reset the phone before logging in with another account.

[__jal]

1) That is a false statement. [1]

2) Even if that were true, that is not what happened in this case.

3) Even if that were true, it still does not explain the weird random data leakage.

[1] https://support.apple.com/en-us/HT203983

[H4CK3RM4N]

But did you reset the phone before handing it over?