You might tell them someone is texting you the math assignment or that you want to call a classmate for help. However, if you’re lying about needing the phone for schoolwork, your parents will probably find out, which could land you in even more trouble. Remind your parents that the phone is important for your safety. Ask them what would happen if they needed to reach you in an emergency and you didn’t have your phone.
Ask for a time limit on the punishment. Then, remind your parents when the time is up.
Respect the limits of the police, as they may not be able to recover your phone, but they will try their best.