My Iphone 6 plus had gotten stolen and the Chip was removed?

So while i was in summer school i had to go to the bathroom, and when i went back to class i didn't realize i forgot it till 30min into class, i ran back to the bathroom, it was gone. I asked some girls that where ditching the last class if they'd seen it. They said that they haven't seen it, they helped me search the bathroom and even let me check their bags and showed me their pockets so i would know it wasn't them. They then another girl that was there said that she saw a girl in a red shirt leave the stall with a colorful phone and book it. I went to my teachers and told them what happened and the head teacher told security and the others helped me look for it in ICloud.Turned out she turned it off.So my teachers locked it and everything. I went to my school office to ask to see the video tape that's outside the bathrooms and the security weren't there so i have to return tomorrow. After my friends and i went to a shop a block away from my school and they said that that girl had been there to unlock 'her' phone and the guy had the chip. The way he made sure it was mine was asking the color of my phone and the company. He said he'll give me the video tape tomorrow on the girl… But i want to know… If the Chip isn't connected does that mean Icloud is useless? I mean can't the girl just end up buying a new chip and placing it into the phone and just use the phone? Or is the lock screen still there? I'm new to Iphones and i wouldn't know. I honestly don't know what to do. Any advise?

Sadsadsadad

Call your cellular provider and get the info for your phone (serial #, etc.) Do that As soon as possible. Then call the police and report the theft of your phone. Be sure to tell them about the shop helping her "unlock" it and ask that an officer actually respond (not just an over-the-phone report) since there's an identifiable perpetrator. The store's security camera has the evidence.