I'm positive there are times that passengers know exactly what's going on with and aircraft. Case in point: The only time l flew Southwest. Descending to land, as flaps were being extended, there became a very noticeable vibration, which, from my vantage point was obviously coming from the right inboard fore flap, outboard carriage attach point. The vibration subsided when the flap handle was returned to a lesser degree detent and we landed that way. In that case, the crew only knew they had a vibration associated with flap position and a passenger was able to pinpoint the exact problem area for them.