Caught in the Teenage Drama Web

So I'm a parent of two teenagers, and honestly, I feel like I've become an amateur detective. Last night, I was just checking on them to make sure they were okay when I ended up rifling through my daughter's room, looking for her school bag, but finding notes from friends that made me worry she might be getting involved with some less-than-stellar peers. Now, don't get me wrong, I understand the importance of privacy and trust, but as a parent, there are moments when you just want to know your kids are okay. Should I talk to her about it? Or am I overreacting like a paranoid old fogey? Let me know if any of you have similar experiences.