A dozen years ago, when her girls were young, Karen Kiefer would take them into the basement laundry room with her as she washed, dried and folded, the better to keep an eye on them. Occasionally, a sock would disappear, leaving behind its match. Inevitably, there was a pile of misfit socks collecting dust in their Framingham laundry room: knee socks, men’s dress socks, athletic socks, kids’ socks, baby socks. The girls wondered where the missing socks went. But they were especially concerned about those left behind. “Do you think these socks are sad because they lost their match?’’ Kiefer remembers them asking her.