How can I tell if the phone I sold was factory reset?

Hello,

Yesterday I upgraded my phone. Instead of purchasing it online and doing it all myself, I went into a Verizon store and did it with an associate there. While going through the process, I recall turning off the find my iPhone on my old phone, but I don't recall us resetting the phone to its factory state. The associate and I kept having to unlock my phone, so theoretically my old passcode has been compromised and I'm concerned all of my files can be accessed if the phone wasn't reset. I don't want to lose any data on my new iPhone, but is there a way to see if the old phone was properly reset?

Edit: I called Verizon and the associate said it was "standard practice" but I'm looking for something more concrete