What should I do in this situation?

I was looking for a book I lost in my mom's room and I found a bunch of sticky notes in a plastic bag. I looked closer and realized it was a song I wrote a year ago on a long car ride. I hid the song in the back of a notebook that I wrote a lot of personal stuff in and now it's in my mom's drawer. This really made me mad. She must have seen the notebook and if it just fell out why didn't she tell me? Instead she took it without a word to me. This makes me feel like I can't trust her. I don't know what to do. Also, a couple months back I found a poem I wrote on her bed. Why would she do this!?