that would certainly happen if the door had been left open.
If the door and window are shut, as is necessary for correct operation of an extractor fan, another factor comes into play.
Water vapour is lighter than air, and rises (hence clouds). The cooler air, entering under the door, will stratify beneath it. So, in still conditions, the warm moist air will rise to the ceiling and be sucked out by the fan, and the cooler, drier air will fill the room like pouring water into a bucket. Or like hot water in a hw cylinder collecting at the top, with cold water beneath it.
I don't know if the OP took my tip about closing the window.
I hope he hasn't been showering with the door open.
If the door and window are shut, as is necessary for correct operation of an extractor fan, another factor comes into play.
Water vapour is lighter than air, and rises (hence clouds). The cooler air, entering under the door, will stratify beneath it. So, in still conditions, the warm moist air will rise to the ceiling and be sucked out by the fan, and the cooler, drier air will fill the room like pouring water into a bucket. Or like hot water in a hw cylinder collecting at the top, with cold water beneath it.
I don't know if the OP took my tip about closing the window.
I hope he hasn't been showering with the door open.