When Rancho San Rafael was subdivided, the related court case was not even listed under the Verdugo name.Instead, it is listed under A.B. Chapman, et al and Fernando Sepulveda et al.
The case is case #1621 and is pretty well described in Minute Book 11 approximately pages 11 to 51.I will add more information as necessary.
The documentation for this case Los Angeles County Court Case is currently housed in the Huntington Library.(All Los Angeles County Court Cases 1850-1880 were transferred to the Huntington Library so that the Huntington Library Archivists could care for the documents.)