I was wondering if somebody could kindly clarify what went wrong on our recent flight from Bangkok to Birmingham, as nobody a Eurowings seems to know.

We recently tried to transfer at Dusseldorf on a flight from Bangkok to Birmingham. On reaching a security check, my girlfriend, a Thai national, wasn't allowed to pass because she didn't have a transit visa. Eventually, we were escorted to the plane but the pilot decided to leave without us, even though the border security officer had repeatedly called the plane and been assured that it would wait for us. We had to get another connection to London 4 hours later and a train home. Our bags were also lost for 5 days.

I've repeatedly called Eurowings, but nobody knows why this happened.

Do you have to go through security when transferring, or did we miss the sign for transfers? On our return flight, the cabin crew member who checked in our bags suggested that we had gone the wrong way and had tried to enter arrivals. I'm fairly certain this wasn't the case as when I asked the the border security officer if we'd gone the wrong way he said no. He said something about the airline hadn't emailed security to obtain her transit visa. Is this what is supposed to happen? As as far as I'm aware, Thai nationals don't need to apply for a transit visa.