Socks?

We went clothes shopping today for the boys, among other things socks were big on the agenda. Why were socks so important? because somewhere in our house, and I'm dammed if I can find it, is a sock black hole. Yes they pass through the singularity somehow and into a dimension inhabited purely by a sock race.... they must do because it's pretty well neigh impossible to find a pair of socks in our house no matter how many I buy! Where else could they go?
Heres another thing about socks.... why do the always come in packs of three or six? Theres seven days in the week, or there were before we went metric and I don't think it's changed, wouldn't seven pairs make more sense, one for each day.