I lost my iphone or could be stolen?

I lost my iPhone in school and I can't find it. I go to a private catholic school from grades pre k to 8th and I don't think anyone could've stolen it but possible. The last time I saw the phone it had 40% battery and when I found out it was missing, my dad called the phone and it said I wasn't taking calls. Also, my dad has a familymap app on my phone and whenever he tracked me, it said there was no signal or it was turned off. Some places in my school doesn't have signal and it's not stolen because if someone stole, the first thing they'd do is to turn it on. We checked the familymap app every hour and they never turned it on if it was stolen. Every staff member was looking for my phone and we can't find it. I retraced my steps and I still can't find it. I tried the Find my iPhone app and my iPhone was never registered on so that's no help. :/

You need to have set up Find My iPhone/iPad on your device prior to it getting lost or stolen. If you did, go to https://www.icloud.com/...cloud.com/ in your web browser. When you log in, Find My iPhone/iPad will immediately begin trying to locate your device. If not, it's better to call your carrier and phone company and ask them to help you block the phone.
To prevent your new idevice from being stolen or lost in the future, I suggest you set up Find My iPhone/iPad/iPod in iCloud on the device and apply some free anti-theft apps like iLostFinder. It will take pics of the thief or finder when she/he tries to open your device and then send the pics to your email.