Luna, a Hall of Fame player in Mexico, would only get one game in the majors. He would go back to AAA, and then to Nuevo Laredo, evidently still under the Cards' control.
We can say that because Luna goes from Nuevo Laredo to Baltimore's AA San Antonio club in this deal mentioned in this article from the Feb. 5, 1957 El Paso Herald-Post..
"SAN ANTONIO, Feb. .5. ~ The San Antonio Missions have signed Guillermo Luna, veteran lefthanded pitcher purchased from the St. Louis Cardinals last fall. Luna worked with Nuevo Laredo in the Mexican League last season."
Luna would have a pretty fair year at San Antonio, but went back to Mexico for the rest of his career.
Luna will always be one of my favorites because of his 1954 Bowman card, which appears to have been painted-by-numbers.