Have you tried the Lincoln Co, TN GenWeb site?Some GenWeb counties are posting records online, and many TN counties are good for that.Post a query regarding the family, you never know who else is out there working on the same line.Have you checked out land and court records in Lincoln Co, TN?Family tradition doesn't always include all the "facts".But, if Larkin owned land, at some point it would have been sold, and to have clear title for the buyer, something would have to be in there about Larkin.Be sure to check land records long after you think he was gone.If land stays in the family, often it is not recorded until it is sold out of the family.If the county GenWeb site has any volunteers who will do lookups (not research) and would check land tax records, see if Larkin's name stays on there, if it disappears and his wife's name shows up on the next year, more then likely she's a widow.
Just checked TX Confederate pension index:
Smith, Larkin Allen # 24933 McLennan Co, TX Smith, Mary A.(wife)# 35432"""
Did your Larkin fight in the Civil War?Maybe the family didn't want to "talk" about a divorce, or maybe there never was a divorce.I would obtain a copy of this pension record, it should help to tell if it is the same Larkin Smith.You might check in TN and see if Cynthia tried to apply for a widow's pension - if she didn't know he was still alive, she might have.
Work on McLennan Co, TX GenWeb site, and post queries regarding Larkin Smith.There is the possiblity these are 2 separate Larkin Smiths, maybe cousins named for the same common grandfather(?)Have fun.