I lost my iPod 4G three weeks ago. Help!

I lost my iPod at my high school. I've asked the assistant principal, searched in my classes, and looked in the lost and found. I can't find it using the 'Find my iPhone' app on my iPad. Also, I can't read the serial number on the receipt because it faded away. If someone knows how I can either get it back or get a replaced one, please help.