It is a very frustrating process with any airline and BA is the same.

Sorry to hear about this. There is no way around the pain or frustration. In short no one actually knows anything for sure.

The audit trail to find out just where the bag is and what is meant to be happening just isn't there and all airline, BA included, just make placating noises (there are several flights later today it should be on one of them) are made without foundation of facts. AMS is not particularly good at processing lost bags as well (AMS forwarded one of my lost bags to the wrong airport)

You just have to get on with life until the bags show up. Very difficult I know.