My mother yesterday somehow lost her phone. I turned on the lost mode from my phone to see if I could locate it but it was offline. Looked at it again today and noticed the phone was turned on and traveling around the city. It looked liked it was turned on at a home and went to several stores last one being a Taco Bell. I also noticed the battery life was real low. It's now off the radar since the battery died. My main question is that if I give my mom my old 5s, would I still be able to use the find my iPhone feature to track the stolen phone? I know if I port her number to the new Micro SIM, the old phone will lose its cellular tracking ability.