Hey guys, OP here! :) So, good news everyone! I'm not dead (yet). Though I almost died laughing at these comments, thanks for making my day! :D I do believe that there is a logical explanation for this odd occurrence. We do have a communal laundry room in my apartment, as many of you have suggested. The strange thing is, we live in a building that only has 8 apartments, and none of us have babies or young children. And I was not doing laundry that day at all, nor do I recall seeing the sock before we left, which was in a very noticeable spot on the floor. I saw it immediately upon our return. Soooooooo ghosts. It's definitely ghosts. *DUN DUN DUUUUUUN* The plot thickens.

it doesn't have to be from a child actually living there, baby or doll socks can get stuck in a sleeve during laundry and move to the next batch through getting caught in the ridges of the washing machine door opening..it could've unsuspectedly fallen out or off said sleeve while you were walking out and you just didn't notice. I wouldn't worry about it. must be awkward though suspecting your partner is trying to insinuate something(you know like: are you trying to say you want one? haha)

You probably shrunk a sock

Or he's cheating on with a little person & before everyone bitches at yes I know a little person who wears baby socks that is where this idea came from