I went to the restroom, and when I came back, she had his cellphone and was standing up at the table.
She began calling his cellphone every 15 minutes, again and again and again.
This is the age of satellites and radars and Google Earth, of cellphone cameras (and cellphone towers) and IP addresses.
A portable telephone that uses wireless cellular technology to send and receive phone signals. This technology works by dividing the Earth into small regions called cells. Within each cell the wireless telephone signal goes over its assigned bandwidth to a cell tower, which relays the signal to a telephone switching network, connecting the user to the desired party.
Note: The proximity to a cell tower is often the key to good reception when using a cell phone.