Having been underneath T5 and seeing the baggage operation. It's amazingly complexed. Thousands of bags are being passed around the terminals every day. It's a tiny percentage that are delayed.
I know how frustrating it is, I've experienced delayed bags myself. When bags are catching connecting flights, it adds to the difficulty of ensuring they reach their flight.
Bags are scanned at the airports at various stages. We can usually tell which container the bag was out in, did it reach the belt, how long it was on the belt etc.
Unfortunately things can go wrong and delays happen.
I've now started to travel with an A4 envelope with my details inside my luggage.
When a bag is delayed, it can sometimes be be used the luggage label has fallen off. Or the bar code has been obscured in some way.
If bags do lose their label, there's a team in LHR who match the description of a bag with the world tracer reports that are generated. You'd be surprised how many "BK22" bags there are.
If a bag is a generic bag, the contents are then matched with reports. Having a list that says jeans, t shirts, socks, shampoo" doesn't make life easy for the bag to be traced.
Specific things like "black diesel t shirt size large with white skull and cross" allow the team to identify bags far easier. I've had claims, where I've asked if they had any books or magazines in their luggage. The bag had been delayed for over 2 weeks. Once I got the name of the book, we found the bag within minutes.
So I know, delayed baggage is a nightmare. If you do have to give a list of contents please try to be as specific as possible. Think of anything that's unusual ( one passenger had a leather whip inside their case) once they told us. The bag was found straight away!
The final carrier is responsible for the claim. They will then have a team employed to see who is at fault and charge whichever airline is at fault.
When you're travelling home and your bag is delayed, you can still claim for certain items. We'd expect people to have clothing. But other things will en considered if they're essentials.
After 21 days, we will then look at covering the full contents.