This poem appeared in a Macmillan reading textbook called Snails to Whales, published in 1989. I picked it up used in a Lafayette, IN thrift store. Emily Wakefield or Mary Bauer, I've got your book if you ever want it back.
Bob Shein is credited as the artist. Long Gone comes from a collection of kid's poems called Zoo Doings by Jack Prelutskey, who also published a collection called Tyrannosaur Was a Beast, illustrated by Arnold Lobel, who you may remember from last week's vintage dinosaur art post.