Air carrier Flight Attendant reported a passenger with a gate checked bag that had been moved to cargo compartment was retrieved because the passenger informed the flight crew that a laptop was in the bag.

Narrative

Boarding was almost complete. Passenger boarded plane with a grey duffel bag in hand and backpack over the duffel bag. I looked at the bag and did not see a tag from gate agent and told passenger that we had room in the bin. While collecting pre departure drinks from passengers in first class; B FA (Flight Attendant) brought up the grey duffel from this passenger and it had a checked tag on the handle. B FA gave bag to the ramp and spoke with him. She informed me that the ramp personnel had tried to take the bag and passenger wouldn't give him the bag. I told B that I looked at the bag and did not see a gate check tag at all hanging down the bag. Passenger held both bags and had to have had the tag hidden behind his backpack he was also holding in his hand at the time of boarding. Ramp put bag under the plane that had been checked by the gate agent. I asked the ramp personnel why he hadn't informed me about the gate checked bag and his exact words were I assumed the bag would be coming off the plane in a couple minutes". During flight; B FA informed me that the same passenger had informed her; that his laptop was in the duffel bag. She told me she had called to inform the captain. I asked B FA if she had asked passenger if there were any Lithium-ion batteries in the bag before she gave to the ramp. She said she did not because it was already gate checked by the gate agent and assumed that the gate agent had already asked the passenger these questions. The passenger stopped to speak to me and the captain when deplaning. At that time; I said to passenger that I didn't see the gate checked bag tag and since he had his backpack covering the handle of the duffel bag he must of had the tag hidden behind the backpack. Passenger said "that would be correct." He admitted the tag had been hidden from me to see. He asked the captain what he should do about his laptop and the captain told him he should speak to the gate agent to have his bag pulled since he had his laptop in it and was connecting on a flight later that day. Passenger said he just wasn't thinking and forgot about his laptop was even in his bag until we got in the air."