After being as nice as I could be, the person who took my phone started using it to make calls. Luckily, my plan has a wide enough coverage area to where it didn't affect my bill.

We sent repeated messages (both voice and text) saying that all we wanted was the phone back, and that a reward was being offered for its return. All the person did was make calls.

What happened to the days where people would find something and turn it in?

Oh well, thanks for the advice, everyone. I spent $350 on another phone today. It was my birthday present.