Found: Children's Horse Book

Searching for my sister. She says 1950's publication. Illustrated. Chapter book. Elementary age? Yellow binding. About a group of children and a missing horse. Maybe titled "The Seven and Sam" ?? Author? It may be even older. She got it from the tiny library that was a branch of the library from the big city 15 mi. away. I remember the books being older. Never anything new. Our town is bigger now and has a lovely library of its own.

Urmston, The seven and Sam.
Searched Google for "Seven and Sam" horse. Looked in Google Images.
https://openlibrary.org/works/OL15718312W/The_seven_and_Sam?edition=sevensam00ur...

Cover: https://www.amazon.com/Seven-Illustrated-Grace-Paull-Urmston/dp/B002BQJU5W/ref=t...

Wow, that was quick. Somehow I never think to Google books. Thank you from me and my sister.