Burn, I wouldn't pout it past being exactly that, a shot in the dark, at least to a certain extent.
If the police can isolate on shift and/or area where these thefts are occuring then pulling in 22 people is not beyond the realms of possibility in order to catch one. Think about it this way. We (the coppers) have deduced that AT LEAST ONE of these 22 people has been stealing from luggage. Now the chances are they will have some of the loot still hanging around somewhere. If we arrest one or two, and don't get everyone or get the wrong people, then the actual perpetrators will have ample time to get rid of any incriminating evidence. It ain't pleasant for the innocent arrestees, but after the real criminals have been caught the rest will be free to go with no charges brought.
I'm not saying this is the scenario, but just one possible reason for the seemingly large number of arrests.