Due to I'll Never Forget My Alphabet at the end of the episode, there was no time to sing The So Long Song.
During the rest of I'll Never Forget My Alphabet, Joe got out of the J box to look at the rest of the letter boxes and Joe says goodbye to the viewers as the train takes off with the J box remaining empty.
In 100th Episode Celebration, a clip of it was seen in "The Songs We've Sung" montage before this aired and was then in the sneak peek.
Joe took the Yo-Yo with him when he skidooed back home. There was another episode titled Blue's Big Holiday where Steve took three things from the skidoo segment. Also in Mailbox's Birthday, Math!, and Blue's Birthday (the three episodes where Steve and Blue skidooed to the present store - in the third mentioned, it was just Steve), the bought products were brought out of the skidoo.