Here's my first time experience with an unusual occurrence that luckily was resolved quickly. This is on our way to Portugal with a transfer at Newark (EWR) to Lisbon. From our home state, we had gate-checked our cabin bags and were told that at EWR, we just need to pick them up at the jetway. This very typical for gate-checked bags.
At EWR, I was standing in the jetway with others to collect our gate-checked bags. Everyone including my husband got their bags except me! I wasn't so much worried that my bag did not make the flight, I'm sure it did. I was more afraid that it was mixed up with checked luggage and would now be at a baggage carousel which means I would have to exit to baggage claim (therefore exit security), and then re-enter the airside of the terminal by going through the hassle of security. I don't want that even though we have a 4 hour layover or so, largely because this is not a burden I should bear but rather should be on the airline's dime (and time) to bring back my bag to me!
The gate agent did suggest perhaps the bag was accidentally taken to baggage carousel and I complained about it. He was very helpful though. He went back into the jetway looking for the baggage handlers. At one point, he took the exit from the jetway to the apron (and I followed along in spite of signs about Authorized Personnel only; yet whatever! I don't care!). Outside, he poked his head into the covered conveyor belt. This is one of those baggage belts that transport bags from the ground to the jetway. Because it's covered (looks like a tunnel) it wasn't immediately obvious if there were still bags in it.
He poked his head into the tunnel, then looked back at me with a smile and said "Is this your bag?" It was! He saved the day! My bag was midway up the conveyor belt. It wasn't stuck. It looked like someone turned off the conveyor belt before the final bag made its way to the top where a ground staff would then hand deliver bag to the jetway. How did this mistake happen?
The helpful gate agent kept shaking his head and said multiple times, "This shouldn't have happened." He looked peeved and picked up his walkie talkie. I don't know what he said but it seemed to me that he was radioing ground staff and making a complaint.
I think if it turned out that the ground staff accidentally delivered my bag to baggage carousel, I would try to make a fuss and say that they need to bring the bag to the gate where my flight to Lisbon will be departing. I shouldn't bear the time cost of exiting airside to landside, and then go through security again. I intend my 4-hour layover in EWR to be time to explore the airport shops and relax, not correct someone else's mistake.