Indeed, I thought about that as well; it is a risk, but I won't have valuables in there, only clothing. The only thing I can think of doing is at check-in for my US flight is to have the IB agent see if my baggage is loaded, probably will do that with the boarding gate agent. I've done this with Swiss connecting from a United flight and they confirmed. I don't know if IB has the ability to check loaded baggage status via their computer system. It is only 2019 after all, and it is Espana.