Looking for Matilda

I am busily planning for a long-awaited genealogy trip.  I will be going to Clay County, Indiana to find proof that Matilda Grass Shuey is the daughter of Robert Grass.  There are some undocumented lineages circulating that this is the case, but no-one can provide proof of their connection.  Robert Grass lived in Clay County from the mid-1830's until his death.  I have searched through everything I can find online and in FHC microfilms, as well as every published book I could find (Madison, Newberry and DAR library).  Hopefully, the Clay County Genealogical Society will have that one obscure proof that I need.  I've been trying to make this trip for a long time, but something always comes up - this time it will happen!