I’m hoping someone can help me find the name, and maybe the author, of a children’s book. It wasn’t very thick, had illustrations, I believe it was published in the 1960s and was aimed at readers ages 6-10. I read it between 1969-1971. 
A young girl was allowed to take a bus trip by herself once school was done for the summer. She may have been visiting her grandmother. She took her doll along. I seem to remember the doll was made of cloth and wore a dress and pinafore. The bus stopped for a rest break, and the girl took the doll with her. She had a chocolate bar at one point and may have bought it during the stop. She got back on the bus but didn’t notice until after it left the rest stop that she left the doll behind. I don’t recall if she got the doll back.
I would appreciate any help finding this book as the memory of it has always stayed with me.