Electronics Repair Questions? Ask an Electronics Technician
Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, it would appear that the missing phone is still within the range of the base unit and was inadvertently left on TALK.
Have you tried on the base unit pressing on the LOCATOR or HANDSET LOCATOR button? ...while somebody listen for a beeping sound from the missing handset