Let's dial this down a bit. Mostly bags get through the system. Sometimes bags get delayed, low percentage, but it happens. Typically they resurface after a few days. You have not seen the bag - it seems - so at this point you don't know what has happened. In a few days, if you go through the usual WorldTracer route, you should be reunited with the bag. It's tedious and there are often complaints about the process, but it tends to work in the final analysis. Air tags help on the information flow, but typically won't get the bag to you any faster, and for some people it adds to their stress level. It sometimes happens that bags are mis-labelled and thus removed after a "onboard" scan, relabelled and rescanned. This is sometimes behind those slightly mysterious comments from the captain in their briefing about "paperwork issues with baggage reconciliation". Usually check-in staff won't touch a bag after they have pressed the button that sends it off down the belt into the baggage warehouse.

Contents going from bags? Yes, very rarely it happens. Rare because if you have a decent job at an airport then being fired and possibly prosecuted for £50 of second hand junk isn't usually a good equation, particularly in places where salaries are high. The TSA have the power to remove things from bags, and occasionally they remove silly things like alarm clocks and theatrical props out of an abundance of caution, but rarely will the sky fall in. If something has been removed under BA's stewardship, which should not have been removed, then BA or your travel insurance will pay up, another bit tedium but it shouldn't let it get to you. One of the few advantages in getting old is understanding how the things that really matter - affection, friendship, family, pets, faith, hope, charity - are usually safe and waiting for us.

By all means seek more help here on luggage tracking and follow up, but it's not too complicated and is explained on the BA website. If you have Property Irregularity Report then you are half way there.