Lou, may sound obvious but was there a preceding aircraft? I was once landing at ORY on a flat calm beautiful summer morning. The previous landing A/C (an A320) had been 7nm ahead on the approach, and there had not been a ripple. As I flared, all hell broke lose in roll and I was compelled to use really gross aileron inputs both ways until, as so eloquently put earlier, "the landing intervened" and we subsided onto the earth in a flurry of feathers.
Medium following a medium with 7 miles between would not have alerted me to a potential wake-turbulence encounter.
Does now though.