How was Jeffrey able to eat spaghetti at the Pickwell's house in "Maniac Magee"?

There are ten Pickwell children, and at dinnertime each day, Mrs. Pickwell opens her back screen door and lets out a distinctive whistle which all the children recognize.   They come running in to eat from every corner of the neighborhood, "from the dump, from the creek, from the tracks, from Red Hill".  In addition, the family is of the sort that is "always helping out somebody", so visitors at mealtime are taken as a matter of course.  On the night in question, Jeffrey manages just to slip in with the Pickwell children when they respond to the call to dinner; there are, at that particular meal, in addition to the ten children, "the parents, the baby, three grandparents and great-grandparents, and "a down and out taxi driver whom Mr. Pickwell was helping out" seated around the Ping-Pong table where Mrs. Pickwell feeds spaghetti to her "small nation".  Accustomed to commotion and extra mouths at suppertime, and no one thinks to ask who "that kid" is until after the meal is over. 

When Dominic Pickwell does finally think to inquire of his brother as to the identity of the kid who sat next to them at the table, Jeffrey is long gone.   The Pickwell kids each figured that he was the friend of one or the other of their many siblings, and by the time they realize that no one actually knew the quiet visitor and rush out to see where he went, they can only catch a glimpse of him in the distance, running with a book in his hand along the railroad tracks (Chapter 6).