What to do if my ipod is stolen?

My ipod was stolen during period 3 yesterday in the library. I lent it to my friend to play with. I know he isnt meant to play on it but i didnt mind if he played. As long as i wasn't blamed for it. After about 45 minutes into the period he put it onto his table and started looking at another guy playing tetris. I didnt notice he just put it down. The weird thing is it got stolen DURING the lesson, no one approached me and my mates group of tables except for the teacher (dont blame her :P) and it was stolen? I searched my friend and the people sitting near him he couldve passed it to. I searched him his bag and there bags and there person but to no success. I know it isnt lost because this happened when we were in the library and the library always searches the place after school. I searched all over the floor and all over the library (literally) but again to no success. I filed a complaint to my stage head teacher (who by the way was pissed at me for my friend playing on it) and said shed ask the office to let her know if anything turned up. I decided that wouldnt be enough so i went to the deputy principal who is very nice to me and she said that she'd put a note in the student news and talk to the people sitting near me and my friend during that lesson. My other friend (yes i have more than 1 xD) suggested we ask the people who were sitting near me if they had ipods and then call those peoples parents and ask them if they have bought there child an ipod. We thought that was a good idea so i think the deputy is going to do that... i have no tracking software on it. I also want to know if i should tell my mum or wait a week or so in case it shows up before i give my mum a heart attack. If you think i should tell my mum please tell me how i should bring it up! Thank you so much!