For any of you that are interested I thought I'd just give you an insight as what happens when cases go missing.
When a case is reported as missing at the airport the 'tag' number that was given at check-in is entered into the baggage tracing system along with other details such as size,colour,make etc. Similarly, the info of any unclaimed bags that are left on the belt is also entered and the computer automatically tries to find matches based on this info. In the majority of cases, the computer is able to find a match and a message is sent to the handlers where the bag has been claimed as lost. The handlers then correspond with whatever airport/airline is holding the lost bag to organise for it to be delivered. Naturally, the time it takes to get your bag back will depend on where the bag is found. Furthermore, lost bags are treated as excess luggage, so if the next flight is up to its weight limit, then the bag will be delayed further until there is space available.
If no 'automatic' matches are generated by the computer within the first 7 days or so, then the handlers will probably assume the lost bag is 'tagless'. This means that sometime after the bag was checked in the tag has been torn off, so no-one knows where that bag should be going. If this happens, the handlers will try to find a match based on the other information given (colour, shape, size, make etc.). Any airport/airline holding bags similar to the description then send messages to the handlers. If the bags are fairly unique then they will be send on as before. However, if the case is fairly common to many others, customers will be asked to provide examples of items in their case and the unidentified case will be forced open to see if these items match.
Lost bag files remain 'active' for 3 months, after which the customer can make a claim against the airline. The claim is limited to the weight of the case at check-in, so a customer will be awarded X pounds per kilo (I don't know what the current rate is, but it is standardised across all airlines). Even after this happens however, lost bag files are never 'closed' and there have been situations where bags have turned up years after they were lost. In this instance, the cutomer still gets their bag back, and does not have to pay back any compensation received.
Tips for travelling....put your own label on the bag as well as the one given at check-in. The more unusual the case, the easier it is to identify. Stick a label with your name and address on the inside of the case so it can be easily identified if forced open.