Why the tag disappears
Three things account for almost every missing tag. The piece has been reupholstered, in which case the new fabric carries no code at all and the original one is irrelevant because it described a fabric that is no longer on the frame. The tag was cut off, usually by a previous owner who assumed it was a scratchy label rather than technical information. Or the furniture predates the coding convention entirely, which covers a great deal of genuinely old and inherited furniture. None of these mean the piece cannot be cleaned; they mean the shortcut is unavailable.