I think you'll find the pilots had no visible clues as to why their engines stopped. Hardly right through the plume then….
You don't think them not seeing the plume might have been something to do with it being dark at the time? They certainly flew over the immediate vicinity of the volcano in the initial plume, not thousands of miles away in a dispersed cloud, and far from there being no other clues, smoke entered the cabin and there were other unusual visual signs on the windshield and the engine intakes.
I note your military jets with engine damage, but then military jets don't fly the same flight profiles as commercial aircraft, so you can't make a direct correlation – in any case damaged engines post flight is hardly a mid air incident of the scale suggested for flying through an ash cloud. I'm not denying there is an issue, just trying to add a bit of realism to the drama people are making of it.
Of course the original claim was wrong anyway – I'm aware of 3 flights that have gone directly into plumes, and in every case they lost engines, so that's 100% failure rate for planes doing that (which doesn't necessarily bear any relation to flying through the ash cloud above us right now).