The narrator’s explanation to his preteen son pretty much sums it up.
Okay, a spacetime warp. It’s formed by the interaction of the complicated magnetic field from the motor, and the rotation of the drum. The metal drum picks up an induced field and right in the center, a spacetime vortex forms. Any sock falling through disappears.

Variants

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  1. “The Sock Problem” by Alastair Mayer, in Analog, October 2011.
  2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . written by Alastair Mayer