Yup. "Rich Kid's Rag" WAS included in the early workshops of FOSSE, but was eventually not included in the show at any time. FOSSE did contain a few more numbers during its pre-Broadway out-of-town tour/tryout ("The Alley Dance" from MY SISTER EILEEN; "Beat Me Daddy, Eight to the Bar" from BIG DEAL, and others), but the "Rich Kid's Rag" was never included.
For what its worth... being a huge ardent fan of Bob Fosse and his work since childhood, I was sourly disappointed with FOSSE. Having several friends in the cast since its conception, seems many in the original cast weren't happy with the show, either. During the work-shopping stage of the show, they viewed hours and hours of sensational footage of Bob Fosse's work and many were confused with what was being used and what was not being considered for the show. Also, the show not having any form of narrative or 'host' left many in the audience confused as to what number was from what, etc. I personally would have loved FOSSE to have used the original set and costume design for the numbers represented, ala JEROME ROBBINS' BROADWAY.
Anyway... back to the topic at hand -- several years later (in 1966), Bob Fosse used elements from the "Rich Kid's Rag" for the "Rich Man's Frug" in SWEET CHARITY.
Here is the original Broadway cast of LITTLE ME performing the "Rich Kid's Rag":