LOST MY PHONE AT SCHOOL?!?!?

Kso at my school we had a school wide event and alot of kids stayed after until 4:40. The event took place right after school and it involved running. So i went into the bathroom to change, then i was rushing to get outside to make sure I didn't miss the event. My phone was in my back pocket in my jeans. But i had to change into shorts, so i took my phone out and put it on the toilet paper holder. Then, i ran outside and ran without putting my phone back into my bag. Then i realized i didn't have it about an hour later. Then i told my bestfriend and we went back to the bathroom and looked. It wasn't there.... Then she told my ex-boyfriend about it and he said that some girl GAVE MY PHONE TO HIM. Then i asked him what he did with it. Then he sad he handed it into some lady. He described her and thought she was a teacher. But there were alot of parents at the event too. I went to the main office and asked if anyone turned it in, and they said no. My ex-boyfriend looked for the lady again, but didn't find her. I spent an hour and a half looking for it and had the school make several announcements over the loud-speaker. I don't know what to do. I had 356 contacts and pictures of me and my friends. I don't know if some freak has my phone now or if a teacher does. WHAT SHOULD I DO ?!