Yes. If a big market one expects to be under attack reports fending off attack, then one would be more optimistic about it:

Hence, observing BMR silence pushed the infiltration outcome to a high posterior while the not-trying remained still pretty unlikely. Of course, for an obscure small marketplace, the reasoning would happen the other way around: because it starts off more likely to be ignored than infiltrated, silence is golden

(That said, that only applies to the one particular kind of observation/argument from silence; as I told Chen, there were several reasons to expect BMR to be short-lived on top of the general short-livedness of black-markets, but I think the logic behind those other reasons doesn't need to be explained since they're not tricky or counterintuitive like the argument from silence.)