The answers here do not address the possibility of the DOP effect (Disappearing Object Phenomena) being touted on the Internet these days. Obviously the missing sock is 1) stolen by a poltergeist (which I find unlikely, because I would imagine you’d see the sock floating out of the room), or 2) temporarily exiting into an alternate universe.

Many scientists do believe the possibility of parallel universes. The evidence suggests this is proof that small portholes open up and swallow your stuff, then later spit them out behind the washing machine due, most probably, to a slight perturbation of the spacetime continuum. Such ripple effects might be caused by perfectly explainable phenomena like solar flares or gravity from passing celestial bodies.

There is a third explanation, though highly Steven Spielbergish. There could be unseen Gremlins hiding in your wall that come out and steal stuff when you’re not looking. This would provide them with clothing and blankets. Ask any Mom. But I don’t want to make light of this most serious question.

There are many anecdotal stories of the DOP effect in real life, and as we all know anecdotal stories are the stuff that science is made from. Where there is smoke there’s fire. When stuff disappears, it’s not you. It’s paranormal.