As for no PA's, well I can assure you that there were probably plenty of "ding dongs" going on in the galley in the minutes prior to the evacuation being called as crew and flight deck discussed the situation via the interphones.
Exactly.
Plenty of "ding dongs"
Which makes people think that something must be up, but - not having a ding-dong dictionary to hand - were unable to determine exactly what.
Very clear communication....