Gofer...
If the aircraft flew through another aircraft's wake, it will make a jolt enough to startle the Flt Crew, let alone the PAX! I make a point of making a PA is this happens, but maybe not all do...
It is also possible, in negotiating their dinner / the Telegraph crossword / laughing at the latest Mgmt edict, someone's foot slipped off a foot rest onto a rudder pedal. I'd still have made a PA - and blamed the above turbulence!
To be honest, if the Cabin Crew continued without batting an eyelid, I wouldn't worry...
NoD
(BA A319 Capt)