You apparently mistook classmates for "friends." A good administrator would get to the bottom of your problem, and some parental contact might help the situation. But, as a previous post pointed out, after you buy a new camera, be sure to never let it out of your sight if you choose to bring it to school again. This is why many expensive electronic items are forbidden from being brought to school: It's too big of a temptation for dishonest classmates and wannabe thieves.
Since the person who ended up with it may not know who it belongs to, I suggest first telling the coach and then asking for an announcement to be made at that debate or the next debate. You can also post an announcement in the school paper.
Probably, you are going to have to buy a new camera. But with something that big, you might get lucky. Someone might feel bad about taking it. So I would start by going to the school office and asking for it. Then I would ask the school if someone could announce that I lost my camera and ask for it to be returned. If all else fails, maybe offer a reward?
But all this not works THEN!!!!
You are at backstage preparing for your debate. You know that the thiefs are of your school but you do not know who they are. You gave your camera to your friend to make ur video but she gave the camera to someone else. When you go to that person to whom your friend gave your camera she said to you that she returned it to your friend,but when you again went to your friend she says that she does not have the cammera or she doesn't have it from her. What will you do in that situation when you can not blame on your friend neither on the other person cuz you do not know who is the thief.