Couches are weird, really weird. You can lose a lot of things inside a couch. Most children believe there are monsters in the couch, having grown up and learned there is no such thing as monster, so I have decided that the cause must be a black-hole. Seriously, couches consume everything, the things you can find when you look through your couch. This Infographic describes how these eating machines are made.
Image from fatlosshaven.com