Money help.?

I'm in BIG trouble! My friend gave me his his iPod at told me to fill it up with songs on the weekend. On monday someone stole the iPod from my locker. My friend doesn't know and he's not goin to know. I bought an exact iPod for my friend, he hasn't noticed. Well my mom saw how much money I have and if she sees my treasury (an envelope full of cash) she'll know I'm missing about $200. I only have $10 bucks to spend, I need a new I.D. card which costs $5, and I need to pay $10 for the PSAT. I don't want to ask my mom for the money because she'll say don't you have money?? and then she'll ask to see my money. My mom can't know! She is very dominate, like 10X more than my dad. If I tell her what happened she'll call me stupid and she is the kind of person that doesn't believe in being a good friend when it can hurt you. Well what is a good excuse to tell her that I don't have anymore money? Or better yet, how can I make $20? My dad is cool, maybe he can help.