Baggage loss statistics
If you wonder why your baggage got lost this time, then the Association of European Airlines is a good source, with its statistics about punctuality, lost luggage, and a timeline of events. In their consumer report for the second quarter (found on flyertalk) , the number of times that Heathrow's baggage system simply broke down -- independently of any well-known external difficulties such as terrorist attacks -- is striking, and scary.
Unsurprisingly, British Airways ends up on the last place (23 out of 23) in the baggage handling discipline, "delaying" 28 pieces of checked baggage per 1,000 passengers. To put that number into perspective and see just how far an outlier it is, Swiss was on place 10 (losing 10 pieces per 1,000 passengers), Lufthansa on place 16 (losing 16 pieces per 1,000 passengers -- the European average), Air France on place 18 (losing 16.3 pieces), and KLM on place 21 (losing 17.8 pieces).
In the first quarter, BA had performed slightly less miserable (place 23 out of then 24, and ahead of TAP which is place 22 in the second quarter), losing "just" 24.7 pieces per 1,000 passengers, without any reported baggage system failures at Heathrow.
Note that, when comparing lost baggage numbers, some care is needed: missing baggage reports are taken by the last airline in a chain of connections. Yet, I'm guessing that numbers for the likes of BA, LH, AF and their recent acquisitions are roughly measuring the same kind of experiment, given that all these airlines have lots of connections and large networks.
On the other hand, numbers for some other, smaller airlines are likely to be distorted heavily, and don't lend themselves to an easy comparison. For example, it might seem surprising that an airline like Luxair (which does pretty much exclusively point-to-point traffic between Luxembourg and the rest of Europe, plus some holiday destinations, and should therefore have very little lost or delayed luggage) ends up on place 19 (losing 17.7 pieces of luggage) for the second quarter -- but then again, they provide feeder services for Lufthansa in Frankfurt and Munich, for BA (and others) in Heathrow, and for Air France at Charles de Gaulle.