"RESERVED” church ledger or register?

We’ve run into a challenge I’ve never encountered before. Does anyone have experience finding records from a “RESERVED” church ledger?

I’m helping a cousin research a possible mutual relative, Maria Guadalupe Romo, born 12 Dec 1893, daughter of Margarita Pedroza and an unknown assailant.

We have a civil registration in Encarnación de Díaz, Jalisco dated 13 Dec 1893, for a Maria Guadalupe, no surname or parents listed. Her mother was from this area. The other hint that we’ve found the right record is that a corresponding baptismal record 14 Dec 1893 mentions that the names of the parents and grandparents are listed in the "reserved book." I suppose a child born of a criminal act might qualify for this kind of confidential treatment.

Can someone advise how we might to get information from the reserved book? Does anyone have historical contacts in Encarnación de Díaz that might assist?

This research is for an elderly aunt who is getting up in her years. We would really like to help her shed more light on her family history, including this ancestor, her grandmother.

Replies here or to myclue4u@mac.com are greatly appreciated.