I'm grounded for three days: what should I do?

Okay, so I got really frustrated and said "fu*k!" to myself. My cousins (who are MAJOR snitches) heard me and squealed on me. So then I got lectured by my mom and my aunt. My mom took my phone away until Friday morning. That's the problem because my mom freaks out if I talk to guys on the phone, and I'm scared that she'll look through my phone now that she has it. And I don't do sexting. I just talk to my guy friends normally and sometimes flirt and tease each other. Nothing inappropriate. I'm just scared that she's going to look through it and see my contacts and messages. She's really paranoid about these kinds of things. So I get grounded for saying the f-word. It's so annoying having cousins who are goody two-shoes. They are going to see and hear things way worse than the f-word. I understand it was irresponsible of me, and I did apologize. I'm just really scared of my mom snooping around with my phone. Please help! I'm 15, btw.