Does this girl have my iPhone?

For Christmas my mom bought me the iphone 6 I had it for about 2 weeks before it was stolen at school. Unfortunately I couldnt track it with Find My iPhone so I was assed out. Now I'm starting a new year at school and recently a girl I know and hang out with (who was a student here before) recently enrolled back in school and she has an iphone 6 in the exact same color mine was. She also hangs out with the guy I suspected stole my phone. Of course you can't just go around like a crazy lady like " I had that same one so that must be mine!" but I noticed her phone had the same exact crack mine had before It went missing. I want to know if it's my phone and I have a crazy gut feeling that it is. I dont want to insult her or anything, I just want to know is that's my phone forsure and If it is I want it back. but in order to do that I need to find this out first - SO BACK TO THE REAL QUESTION .. is there any type of way that I can check like a serial number or something to verify that it is in fact my phone? Like if she goes to the settings and goes to the info about the phone would something that can help me be on there? I have the original box with everything that it came with and I was hpoing that it could somehowww help me. I don't know what to do, but I want to do something bc the thought is bothering me.