B737 Next Generation Undifferentiated
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 117; Flight Crew Total 359; Flight Crew Type 359
Other / Unknown
Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Security
Human Factors
I left a personal item on the flight deck that the following crew thought may have been a security threat. We landed and parked the aircraft without incident. We departed the aircraft to change planes for our next flight. While standing at the outbound gate; the Gate Agent said there was someone on the phone asking for me. When I answered the phone; it was the Captain who was taking the aircraft we had just deplaned. He asked me if I was missing the battery pack for my noise canceling headset. I do have a noise canceling headset that uses an external battery pack; but I was unsure if I missing mine or not. So I replied it was probably mine and I would return to [the] gate to sort it out as we were still waiting for our aircraft to arrive.When I arrived at the gate; the outbound crew; the Ground Security Coordinator; and myself spoke briefly in the jet bridge. I was able to identify the battery pack as mine. I then learned that it had not been discovered until close to departure time and it caused a delay trying to identify what it was; who it belonged to; and if it was a threat the safety of the flight. After I was able to identify the battery pack as mine and I just plain forgot it on the plane. It was deemed not to be a threat and the flight departed 16 minutes late.
B737 NG First Officer reported leaving a battery pack on an aircraft which caused a security incident with the incoming crew.