What is the nature of the close call the narrator and the old man have with the Memory Police in Chapter 23?

When the narrator and the old man travel to the narrator's mother's cabin, they time their excursion perfectly in order to be back by dark, but when they arrive at the train station, the train has still not arrived. They are then horrified to discover that the Memory Police are at the train station searching all of the passengers' bags. While they are still in line, a young woman collapses from exhaustion and it creates enough of a commotion that the Memory Police get everyone else through the line in a hurry, foregoing the bag checks entirely for a few passengers, including the narrator and the old man.